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Cummins/Onan 4BT3.9-G4 Engine

The Cummins/Onan 4BT3.9-G4 is a 3.9 L 4-cylinder turbocharged engine rated at 1800 rpm, producing up to 73.9 kW. It powers generator sets from Cummins/Onan, including the 40DGCA, 42DGCG, 50 DGCA and 50DGCB. It holds 10.9 L (2.9 gal) of oil and 16.9 L (4.5 gal) of coolant.

Also known as: 4BT3.9G4, Cummins 4BT3.9-G4

Part of the Cummins/Onan 4BT3.9 engine family — 8 variants share parts & fitment.

3.9 L

Displacement

Cylinders

1800 rpm

Rated speed

73 kW

Gross power

On this pageSpecs Generator sets Maintenance FAQ Service intervals Torque & specs Fluids Fault codes Procedures Wiring

Engine specifications

Oil capacity	10.9 L
Coolant capacity	16.9 L
Displacement	3.9 L
Cylinders	4
Aspiration	Turbocharged
Rated speed	1800 rpm
Gross power	73 kW

Generator sets powered by this engine

Cummins/Onan 40DGCACummins/Onan 42DGCGCummins/Onan 50 DGCACummins/Onan 50DGCBCummins/Onan 51DGCHCummins/Onan 60 DGCB Cummins/Onan C50 D6 Cummins/Onan C65D6 Cummins/Onan C70 Cummins/Onan C70D5 Cummins/Onan DGCB

How to read your Cummins/Onan engine serial & model number →

Common problems

The FAULT 1 or FAULT 2 fault lamp lights. Engine shuts down immediately, engine runs for several seconds and then shuts down, or engine continues to run FAULT 1
Cause: The standard undesignated fault functions are programmed to shut down the set when a fault is sensed. Fault 1 is time delayed while Fault 2 is immediate. The nature of the fault is an optional selection that is determined when the set installation is designed. The undesignated fault functions may also be programmed for non-shutdown or non-time delay
Engine cranks but will not start
Cause: Empty fuel tank, fuel leaks, or plugged fuel lines
Fix: Correct as required
Over Current 1471
Low Coolant Level 197
Cause: Engine coolant level has fallen below the warning trip point
Fix: If generator is powering critical loads and cannot be shut down, wait until next shutdown period, then follow code 235 procedure; if engine can be stopped, follow code 235 procedure.
Low Battery Voltage — Battery voltage is low 441
Cause: Damaged battery cable connections
Fix: Inspect the battery cable connections for loose connections and/or corrosion, and repair as necessary
Excitation Fault (Loss of AC Sense) — The control has lost voltage sensing or has lost zero cross sensing 2335
Cause: Incorrect configuration
Fix: Make sure that values for the Low of AC Voltage Threshold (85%) and Low of AC Voltage Time Delay (10 seconds) are correct in calibration
Engine Oil Pressure Low (Shutdown) — Engine oil pressure is below the low oil pressure shutdown threshold (35 psig) 415
Cause: Lubricating oil level is low
Fix: Check the oil level. Add or drain oil, if necessary
SWITCH OFF lamp flashes
Cause: Indicates Run/Stop/Remote switch is in the Stop position which will prevent automatic starting if an automatic transfer switch is used
Fix: Move the Run/Stop/Remote switch to the Remote position for automatic starting
PRE LO OIL PRES lamp lights. Engine continues to operate
Cause: Indicates engine oil pressure has dropped to 20 psi (138 kPa)
Fix: If generator is powering critical loads and cannot be shut down, wait until next shutdown period and then follow step 5 procedure; if engine can be stopped, follow procedures in step 5
PRE HI ENGINE TEMP lamp lights. Engine continues to operate
Cause: Indicates engine has begun to overheat and engine temperature has risen to approximately 215°F (102°C)
Fix: If generator is powering non-critical and critical loads and cannot be shut down, reduce load if possible by turning off non-critical loads; check air inlets and outlets and remove any obstructions to airflow; if engine can be stopped, follow procedure in step 3
LO OIL PRES lamp lights. Engine shuts down
Cause: Indicates engine oil pressure has dropped to 14 psi (97 kPa)
Fix: Check oil level, lines and filters; if oil system is OK but oil level is low, replenish; reset control and restart; contact an authorized service center if oil pressure is not in the range of 25 to 40 psi (172 to 275 kPa)
LO FUEL LAMP lights. Engine shuts down and LO OIL PRES lamp lights
Cause: Indicates engine has run out of fuel
Fix: Check fuel level and replenish as required
LO FUEL lamp lights. Engine continues to run
Cause: Indicates diesel fuel supply is running low
Fix: Check fuel supply and replenish as required
LO ENG TEMP lamp lights. Set is in standby mode but is not operating. (Lamp lights when engine coolant temperature is 70°F (21°C) or lower. Since the lamp goes out after the engine warms up, there should be no cause for alarm even during initial generator set operation.)
Cause: Indicates engine coolant heater is not operating or is not circulating coolant
Fix: Check for the following conditions: coolant heater not connected to power supply, check for blown fuse or disconnected heater cord and correct as required; check for low coolant level and replenish if required, look for possible coolant leakage points and repair as required; contact an authorized service center for service if none of the above
HI ENG TEMP lamp lights. Engine shuts down
Cause: Indicates engine has overheated (engine temperature has risen above 222°F/106°C) or coolant level is low (sets with coolant level sensor)
Fix: Allow engine to cool down completely before proceeding with the following checks: check coolant level and replenish if low, look for possible coolant leakage points and repair if necessary; check for obstructions to cooling airflow and correct as necessary; check for a slipping fan belt and tighten if loose; reset control and restart after locating and correcting problem; contact an authorized service center for service if none of the above

Compiled from service & troubleshooting documentation across every generator set that uses the Cummins/Onan 4BT3.9-G4.

Maintenance schedule

Item	Spec	Capacity	Part #	Interval
Air filter	Normal duty air filter		0140-3765		Amazon eBay
Fuel filter	Single spin-on canister, full flow		—	500 hr
Oil filter	Single spin-on canister, full flow		—	500 hr
Battery	Battery capacity (1x) 75 A/h		—
Belt			328876800		eBay
Coolant	Coolant capacity (only engine)	7.2 l	—
Oil	104oF (40oC) ambient radiator	11.5 L	—	1000 hr
Spark plug	Not applicable		—	1000 hr

Pooled from every document that names this exact engine — confirm the interval and part number against your unit's serial number.

Service intervals

Item	Action	Hours	Notes
Charge air piping	Check	50 hr	Daily or after 8 hours
Coolant level	Check	8 hr	Daily or after 8 hours
Exhaust system	Inspect	8 hr	Visually and audibly inspect the exhaust system daily for leaks per the maintenance schedule; check for corrosion, obstruction, and leaks every time you start the generator set and every eight hours when you run it continuously
Fuel Filter(s)	Drain	8 hr	Drain 1 cup or more of fuel to remove water and sediment. Refer to engine operation and maintenance manual for procedure.
Fuel Tanks (water and sediment)	Drain	8 hr	Drain 1 cup or more of fuel to remove water and sediment.
Fuel level	Check	8 hr	Daily or after 8 hours
General genset inspection	Inspect	8 hr	Daily or after 8 hours. Check for oil, fuel, cooling and exhaust system leaks; check exhaust audibly and visually with set running.
Inspect Genset	Check	8 hr	Check for oil, fuel, cooling and exhaust system leaks. Check exhaust system audibly and visually with set running and repair any leaks immediately.
Oil Level	Check	8 hr	Keep oil level near the dipstick high mark without overfilling.
Вентиляционные устройства генератора	Check	10 hr	10 часов / еженедельно
Весь агрегат	Test	10 hr	Включение минимум на час, предпочтительно с нагрузкой 50 %; 10 часов / еженедельно
Подключение вспомогательной клеммной коробки	Check	10 hr	10 часов / еженедельно
Уровень охладителя воды	Check	10 hr	10 часов / еженедельно
Уровень смазочного масла в двигателе	Check	10 hr	10 часов / еженедельно
Уровень топлива	Check	10 hr	10 часов / еженедельно
Уровень электролита в батарее	Check	10 hr	10 часов / еженедельно
Air cleaner restriction indicator	Check	24 hr	If service indicator shows red, replace air cleaner elements and reset indicator.
Coolant level of radiator(s)	Check	24 hr	Top up with Cummins recommended coolant mix if low.
Engine oil level	Check	24 hr	Top up with recommended oil if low.
Fuel level in fuel tank	Check	24 hr	Refill as required.
Fuel lines and hoses	Check	24 hr	Check for leaks, worn or damaged hoses.
Generator set enclosure	Inspect	24 hr	Walk-around; ensure no inlets/outlets covered.
Operator panel operation	Check	24 hr	Check display; replace component if not functioning.
Air Cleaner	Clean	50 hr	Clean if required. Perform more often in dusty conditions.
Air cleaner (clean if required)	Clean	50 hr	Weekly or after 50 hours; perform more often in dusty conditions
Air intake system for leaks	Inspect	50 hr	Visually inspect; check audibly when running.
Battery charging system	Check	50 hr	Weekly or after 50 hours
Battery connections	Check	50 hr	Verify connections are secure.
Charge alternator	Check	50 hr	Check visually and audibly when running.
Coolant heater	Check	50 hr	Weekly or after 50 hours
Coolant lines and radiator hoses	Check	50 hr	Check for leaks, wear, and cracks.
Cooling fan blades	Inspect	50 hr	Visually inspect through guarding.
Crankcase Oil	Drain	50 hr	First service — Break-in: drain and replace the crankcase oil after the first 50 hours of operation on new generator sets.
Crankcase oil	Change	50 hr	First service — Drain and replace the crankcase oil after the first 50 hours of operation on new generator sets (break-in)
Drive belt condition and tension	Check	50 hr	Check for wear or slippage.
Engine oil and filter	Change	50 hr	First service — Drain and replace crankcase oil after first 50 hours on new generator sets
Exhaust components and hardware	Check	50 hr	Visually inspect; check audibly when running.
Exhaust condensate trap	Drain	50 hr	Weekly or after 50 hours
Radiator air flow	Inspect	50 hr	Check for blockage, debris, wear or damage.
Water and sediment from fuel tank	Drain	50 hr	Weekly or after 50 hours; drain 1 cup or more of fuel to remove water and sediment

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Service specifications

Type	Item	Value	Unit	Condition
Clearance	Float switch lift below C-clip stop	1/8	inch (3 mm)
Clearance	Overspeed switch magnet-to-fly arm air gap (minimum)	0.005	inches (0.13 mm)
Gap	MPU sensor tip to ring gear teeth clearance	0.5 - 0.6	mm
Gap	Mechanical overspeed switch air gap between magnet and fly arm (replace switch if less)	0.005	inches (0.13 mm)
Other	AFLEX-H (shake table test datum)	<=3.200	g	AC156, tri-axial, 5% damping SRS
Other	AFLEX-V (shake table test datum)	<=1.333	g	AC156, tri-axial, 5% damping SRS
Other	ARIG-H (shake table test datum)	<=2.400	g	AC156, tri-axial, 5% damping SRS
Other	ARIG-V (shake table test datum)	<=0.533	g	AC156, tri-axial, 5% damping SRS
Other	AVR DROOP preset at factory	five percent droop at full load and zero power factor
Other	Alternator cooling air flow	41.3	m3/min
Other	Alternator excitation current - full load	2.2	amps
Other	Alternator excitation current - no load	0.5	amps
Other	Automatic stop delay after normal power source returns	about 15 minutes	minutes
Other	Battery electrolyte corrected specific gravity (fully charged)	1.260		electrolyte temperature corrected
Other	Battery electrolyte specific gravity, fully charged (corrected)	1.260		corrected to 80 °F (27 °C)
Other	Battery recharge threshold specific gravity	1.215
Other	Battery specific gravity recharge threshold	1.260	specific gravity	recharge if below
Other	Battery specific gravity temperature correction	four gravity points (0.004) for every ten degrees above 80 F (27 C)
Other	Battery specific gravity, fully charged	approximately 1.260	at 80°F (27°C)
Other	Combustion air flow - standby	20.9	m3/min	standby rating
Other	Coolant level below radiator cap opening	2	inches
Other	Coolant level below radiator cap opening	about two inches (50 mm)	mm	cold engine
Other	Cooling system air flow	248	m3/min	standard set-mounted radiator
Other	Cycle crank crank and rest time	7 to 20	seconds
Other	Cycle crank number of cycles	3, 4, or 5
Other	Cycle cranking - number of starting cycles	1 to 7	cycles
Other	Cycle cranking option	15	seconds	15 s crank, 15 s rest, 3 cycles
Other	ECM fuse F1 (starter solenoid circuit)	20	amps
Other	ECM fuse F2 (fuel solenoid circuit)	20	amps
Other	ECM fuse F3 (continuous B+ to remote circuits)	15	amps
Other	ECM fuse F4 (ECM circuits)	5	amps
Other	ECM fuse F5 (engine gauge circuits)	5	amps
Other	Exercise period	at least once a week for a minimum of 30 minutes with load	minutes
Other	Exhaust flow at set rated load - standby	33.3	m3/min	standby rating
Other	Fault current regulation (max output current on any phase under fault)	3	times rated current	single and three phase faults
Other	Flywheel teeth (Teeth Pulses Per Revolution)	110		PCC setting
Other	Frequency adjustment range	±5%	%	genset running
Other	Full load acceptance - frequency dip / recovery time	12.6% / 3.7	% / seconds	NFPA 110 single step load
Other	Full load acceptance - voltage dip / recovery time	29.1% / 3.2	% / seconds	NFPA 110 single step load
Other	Full load rejection - frequency rise / recovery time	3.9% / 2.9	% / seconds	load rejection
Other	Full load rejection - voltage rise / recovery time	18.4% / 1.5	% / seconds	load rejection
Other	Fuse A31-F1 (control B+)	5	Amp	Engine Interface board
Other	Fuse A31-F3 (auxiliary B+)	5	Amp	Engine Interface board; panel lights, run and start relays
Other	Fuse A38-F1 (Network B+)	10	Amp	Governor Output Module
Other	Fuse A38-F2 (Switched B+)	10	Amp	Governor Output Module
Other	Fuse A38-F3 (Governor B+)	10	Amp	Governor Output Module
Other	Fuse TB-Bat F1 (Customer B+)	20	Amp	Engine Harness Assembly
Other	GOV RAMP adjustment range	0 through 10	seconds
Other	Glow plug preheat time	5		glow plug calibration
Other	Glow plug total glow plug time	60		glow plug calibration
Other	Governor droop adjustment range	within 5	percent of nominal frequency (3 Hz for 60Hz sets, 2.5 Hz for 50Hz sets)
Other	Ground fault warning (optional) sensing range	100-1200	amps, time delay 0-1 s	600 VAC class, solid ground
Other	Ground snow load limit	30	psf	For indoor (covered) and outdoor (exposed) installation
Other	Horizontal design seismic coefficient (z/h = 0.0)	1.440	g	Certified seismic design level, IBC Importance IP <= 1.5, Soil Classes A-E, Risk Categories I-IV, Design Categories A-F, SDS <= 2.000 g
Other	Low oil pressure / high engine temperature fault time delay	about 10	seconds	following starter disconnect and inhibited during cranking
Other	Maximum air cleaner restriction with clean filter	3.7	kPa
Other	Maximum surge power	233	kW	PTS test
Other	Motor starting kVA at 90% sustained voltage - PMG excitation	920	kVA	PTS test
Other	Motor starting kVA at 90% sustained voltage - shunt excitation	770	kVA	PTS test
Other	Over current shutdown (51)	>110 and <175	% of rating

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Recommended fluids

Fluid	Grade	Standard	Ambient	Capacity	Notes
Coolant		Refer to Cummins engine Operation and Maintenance Manual for coolant recommendations/specifications			Balanced coolant mixture of water, antifreeze and coolant additives.
Coolant	50/50 coolant solution (50% pure water and 50% ethylene glycol)
Coolant	50/50 coolant solution (50% water / 50% ethylene glycol)
Coolant	50/50 mix of water and antifreeze	Balanced coolant mixture of water, antifreeze and coolant additives			Drain and replace the mixture every 6 months or after 500 hours of operation. Do not add cold coolant to a hot engine; allow engine to cool below 120 F (50 C) before adding coolant.
Coolant	Water/antifreeze mixture				Permanent type antifreeze mixed per supplier for lowest expected ambient; do not use anti-leak additives
Coolant	water/antifreeze mixture			21.0 litres	Capacity with standard radiator 5.5 gallons (21 litres) for 37 DGBA, 35 DGBB, 40 DGBC, 50 DGCA, 60 DGCB; 6.5 gallons (25 litres) for 80 DGDA, 100 DGDB. Do not use antifreeze with anti-leak additives.
Coolant	Смесь воды и антифриза 50/50; низкосиликатный антифриз	Добавка Cummins DCA4 или эквивалент			Вода чистая, без хлоридов, сульфатов и кислот, с pH от 8,5 до 10,5; при заполнении холодной системы остается 6 (максимум 8) % дополнительной емкости для расширения
Engine oil		Refer to Cummins engine Operation and Maintenance Manual for lubricating oil classification			Gensets are shipped with oil added.
Engine oil	15W40			7.9 L (8.35 qt)	Refer to the Engine Operator Manual
Engine oil	5W (Synthetic Oil)	API CC/CD, sulphated ash max 1.85%	below -23°C		Below -10 F (-23 C) and below; pour point 9 F (5 C) below lowest expected temperature
Engine oil	SAE 25W-40				RM92-8M0086227U3 / RM92-8M0086224U3
Engine oil	SAE 5W synthetic	API class CC/CD; sulphated ash content does not exceed 1.85 percent; pour point 9 F (5 C) below lowest expected temperature; viscosity 10,000 mPa s max at -31 F (-35 C) and 4.1 mm2/s min at 212 F (100 C)	below -23°C		For ambient temperature consistently below -10 F (-23 C) with no provision to keep engine warm; do not use petroleum base 5W grade oil
Engine oil	TC-W3	TC-W3			2-cycle outboard oil; RM92-858026QB1U6 / RM92-858027QB1U3 / RM92-858037QB1U3
Engine oil	SAE 10W30 / SAE 15W40 / SAE 20W40 (spec table)		-25°C to 35°C	11.0 litres	Specifications table: Oil Capacity with Filters 11.5 quarts (11 litres) for 37 DGBA, 35 DGBB, 40 DGBC, 50 DGCA, 60 DGCB; 17.3 quarts (16 litres) for 80 DGDA, 100 DGDB. Oil type -13 F to 95 F (-25 C to 35 C) SAE 10W30; 14 F (-10 C) and above SAE 15W40; 32 F (0 C) and above SAE 20W40
Engine oil	10W-30	API CC/CD	-23°C to -10°C		-10 F (-23 C) to 14 F (-10 C)
Engine oil	SAE 10W-30	API Class CC/CD (max sulphated ash 1.85 percent)	-23°C to -10°C		-10 F (-23 C) to 14 F (-10 C)
Engine oil	15W-40	API CC/CD	above -10°C		14 F (-10 C) and above
Engine oil	SAE 15W-40	API Class CC/CD (max sulphated ash 1.85 percent)	above -10°C		14 F (-10 C) and above
Engine oil	20W-40	API CC/CD	above 0°C		32 F (0 C) and above
Engine oil	SAE 20W-40	API Class CC/CD (max sulphated ash 1.85 percent)	above 0°C		32 F (0 C) and above
Fuel	ASTM No. 2 Diesel	ASTM No. 2			Cummins engines on DG series sets normally use ASTM No. 2 Diesel; will operate on alternate diesel fuels within engine manual specifications. Never use galvanized or copper fuel lines, fittings or tanks.
Fuel	ASTM number 2D fuel	ASTM 2D
Fuel	Diesel				Do not use zinc coated or copper fuel lines with diesel fuel.
Fuel	No. 2 diesel				Direct injection fuel system; fuel filter; water separator; automatic electric fuel shutoff.
Fuel	No. 2 diesel fuel				Engine will also operate on No. 1 fuel or other similar fuels; consult engine manufacturer for specific requirements
Fuel	diesel				Do not use zinc coated or copper fuel lines with diesel fuel.
Fuel	Дизельное топливо класса А1 или А2	BS 2869: Часть 1:1998 (класс А1); BS 2869: Часть 2:1998 (классы А2, С1, С2, D, E, F, G, H)			Топливо должно быть как можно более чистым, по возможности не содержать воды и загрязнений
Gear oil	SAE 80W90				LUB11564U12 / LUB11565 / LUB11540U12 / LUB11552U12 / LUB11546
Gear oil	SAE 90W				RM92-858064QB1U6 / RM92-858065QB1U2
Grease	Dow Corning silicone heat sink compound type 340 or similar				Apply to base of replacement diode only

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Fault codes

Code	Name	Meaning	Severity	Action
27	Low AC voltage shutdown	Voltage on any phase has dropped below a preset value; adjustable 50-95% of reference voltage, time delay 2-10 s.	Shutdown	Default 85% for 10 seconds; function tracks reference voltage.
32	Reverse power shutdown	Adjustment range 5-20% of standby kW rating, delay 1-15 seconds.	Shutdown	Defaults 10%, 3 seconds.
51	Over current shutdown	Output current on any phase more than 110%, less than 175% of rating and approaching thermal damage point of alternator.	Shutdown	Control includes algorithms to protect alternator from repeated over current conditions over a short period.
59	High AC voltage shutdown	Output voltage on any phase exceeds preset values; time to trip inversely proportional to amount above threshold. Adjustable 105-125% of nominal, time delay 0.25-10 s.	Shutdown	Default 110% for 10 seconds.
81o	Over frequency shutdown/warning	Adjustable 0-10 Hz above nominal frequency, time delay 0-20 seconds.		Defaults: disabled.
81u	Under frequency shutdown	Generator set output frequency cannot be maintained; adjustable 0-10 Hz below nominal governor set point, 0-20 s delay.	Shutdown	Default 6 Hz, 10 seconds.
101	IDLE MODE	Indicates that the engine is operating in idle mode. Grounding the engine idle input inhibits generator build-up and governs the engine at 800 RPM.	Warning	Grounding the engine idle input inhibits generator build-up and governs at 800 RPM; removing ground returns the genset to normal speed and voltage.
102	EMERGENCY STOP	Indicates local or remote Emergency Stop.	Shutdown	Pull the button out; move the Run/Off/Auto switch to Off; press the Reset switch; select Run or Auto as required. Can only be reset at the PCC front panel.
121	SPEED SIGNAL LOST	Mag pickup speed indication is not being sensed.	Shutdown	Restart and check RPM on digital display; inspect MPU wires/connector pins; check for 3.5 to 15 VAC at MPU while cranking.
135	OIL PRESSURE SENSOR H	Engine oil pressure sender signal is shorted high.	Warning	Check sender/connectors/wires; verify fault simulation not enabled; check 0.5 to 4.5 VDC at P7-13 (OP OUT) and P7-17 (OP COM).
141	OIL PRESSURE SENSOR L	Engine oil pressure sender signal is shorted low.	Warning	Check sender/connectors/wires; check for shorts/open circuits at P7-13, 17, 21.
143	PRE-LOW OIL PRES	Engine oil pressure dropped to an unacceptable level.	Warning	Check oil level, lines and filters; replenish if low; if powering critical loads wait until next shutdown period and follow code 415.
144	COOL SENSOR HIGH	Engine coolant temperature signal is shorted high.	Warning	Check sender/connectors/wires; check resistance between P7-30 (IH20) and P7-34 (IH20 COM).
145	COOL SENSOR LOW	Engine coolant temperature signal is shorted low.	Warning	Check sender/connectors/wires; check for shorts at P7-30 and P7-34.
146	PRE-HIGH COOL TMP	Engine has begun to overheat (coolant temperature risen to an unacceptable level).	Warning	Reduce load; check air inlets/outlets and remove obstructions to airflow; if engine can be stopped follow code 151.
151	HIGH COOLANT TEMP	Engine has overheated (coolant temperature above the shutdown trip point).	Shutdown	Allow engine to cool; check coolant level; check airflow obstructions; check fan belt; check blower fan/remote radiator pumps; reset control and restart.
197	LOW COOLANT LEVEL	Engine coolant level has fallen below the warning trip point.	Warning	Allow engine to cool; check coolant level and replenish; look for leaks; reset control and restart.
200	LOW OIL PRESSURE	Indicates engine oil pressure has dropped to an unacceptable level.	Warning	If generator is powering critical loads and cannot be shut down, wait until next shutdown period and then follow the 201-SHUTDOWN procedure. Access the Oil Pressure menu prior to clearing the fault.
201	LOW OIL PRESSURE	Indicates engine oil pressure has dropped below the shutdown trip point.	Shutdown	Check oil level, lines and filters. If oil system is OK but oil level is low, replenish. Reset control and restart. Oil pressure limits are listed in Table 4-3.
204	OIL PRESS SENDER	Indicates that the control has sensed that the engine oil pressure sender is out of its working range.	Warning	Check that the engine oil pressure sender is properly connected.
210	LOW COOLANT TEMP	Warning occurs when engine coolant temperature is 70°F (21°C) or lower, indicating the engine coolant heater is not operating or is not circulating coolant.	Warning	Check coolant heater power supply, fuse or disconnected heater cord; check for low coolant level and replenish; check for an open heater element by checking current draw of heater.
211	HIGH COOLANT TEMP	Indicates the engine coolant temperature is getting close to the recommended maximum temperature limit: 215°F (102°C) standby or 207°F (97°C) prime.	Warning	Reduce load if possible; check air inlets and outlets and remove any obstructions to airflow; if engine can be stopped, follow the 212-SHUTDOWN procedure.
212	OIL TEMP SENSOR H	Engine oil temperature signal is shorted high.	Warning	Check sender/connectors/wires; check resistance between P7-22 (OIL TEMP) and P7-26 (OIL TEMP COM).
213	OIL TEMP SENSOR L	Engine oil temperature signal is shorted low.	Warning	Check sender/connectors/wires; check shorts and resistance between P7-22 and P7-26.
214	LOW COOLANT LVL	Indicates engine coolant level has fallen below the trip point.	Warning	Allow engine to cool; check coolant level in both radiator and coolant recovery bottle and replenish; look for coolant leakage points; reset control and restart.
215	LOW COOLANT LVL	Indicates engine coolant level has fallen below the trip point. LOW COOLANT LVL Shutdown will not occur if genset is in Idle mode (low coolant warning only).	Shutdown	Allow engine to cool; check coolant level in both radiator and coolant recovery bottle and replenish; if radiator level is low and bottle level correct, check coolant bottle hose or radiator cap; reset control and restart.
220	MAG PICKUP	Indicates mag pickup speed indication is not being sensed or does not match generator set output frequency.	Shutdown	Restart and check RPM on the digital display. Check MPU sender, wiring and adjustment.
221	FAIL TO CRANK	Indicates possible fault with control or starting system.	Shutdown	Check fuse F3 on the Engine Interface board; check for poor battery cable connections; recharge or replace a discharged or defective battery.
222	OVERCRANK	Indicates possible fuel system problem.	Shutdown	Check for empty fuel tank, fuel leaks, or plugged fuel lines; check for dirty fuel filter and replace if necessary; check for dirty or plugged air filter and replace if necessary; reset the control and restart.
223	OVERSPEED	Indicates engine has exceeded normal operating speed (115% ±1% of nominal).	Shutdown	Inspect the mechanical fuel linkage and repair or replace; check the EFC for binding or damage; monitor the PCC duty cycle display and replace A32 or A38 as indicated.
230	LOW DC VOLTAGE	Indicates battery voltage is below 10 VDC.	Warning	Check for discharged or defective battery; check the battery charger fuse; recharge or replace the battery; clean and tighten battery cable connections; check engine DC alternator; check battery charge voltage float level.
231	HIGH DC VOLTAGE	Indicates battery voltage exceeds 32 VDC.	Warning	Check voltage float level on battery charger if applicable (lower float level); check engine DC alternator and replace if normal battery charging voltage is not obtained.
232	WEAK BATTERY	Indicates battery voltage drops below 60% of nominal for two seconds, during starting.	Warning	Discharged or defective battery. See Warning message 230, LOW DC VOLTAGE.
234	OVERSPEED	Engine has exceeded normal operating speed.	Shutdown	Clear fault and restart genset; check fault threshold; monitor RPM; check electronic governor actuator.
235	LOW COOLANT LEVEL	Engine coolant level has fallen below the shutdown trip point.	Shutdown	Check coolant level and replenish; look for leaks; reset control and restart.
240	LOW FUEL-DAY	Indicates day tank fuel supply is running low.	Warning	Check fuel supply and replenish as required.
241	LOW FUEL	Indicates fuel supply is running low.	Warning	Check fuel supply and replenish as required.
250	EEPROM ERROR	Indicates PCC memory error. Data corruption of critical operating parameters.	Shutdown	Perform the Initial Start Setup procedure and save; if the same EEPROM ERROR occurs, replace the digital board (A32).
251	EEPROM ERROR	Indicates PCC memory error. Data corruption of noncritical operating parameters.	Warning	Perform the adjustment procedures and save; if the same EEPROM ERROR occurs, perform the calibration procedures; if it still occurs, replace the digital board (A32).
252	EEPROM ERROR	Indicates PCC memory error. Data corruption of noncritical operating parameters.	Warning	Verify the values or choices selected and repeat the save operation; if the same EEPROM ERROR occurs, replace the digital board (A32).
260	CUSTOMER FAULT 1	Customer defined input closed to ground; the nature of the fault is an optional customer selection which can be programmed to initiate a shutdown or a warning. Default message is editable.	Warning	Isolate the source of the false signal; disconnect the signal lead near the control and reset; if the message drops out there is a short to ground in the external wiring; if it remains replace A34. Customer fault messages are editable.
261	GROUND FAULT	Customer defined input closed to ground; the nature of the fault is an optional customer selection. Default message is editable.	Warning	Isolate the source of the false signal; check the corresponding customer interface board LED; disconnect the signal lead and reset the control; replace A34 or A32 as indicated.
262	RUPTURE BASIN / DAY TANK	Customer defined input closed to ground; the nature of the fault is an optional customer selection. Default message is editable.	Warning	Isolate the source of the false signal; check the corresponding customer interface board LED; disconnect the signal lead and reset the control; replace A34 or A32 as indicated.
263	HIGH GEN TEMP	Customer defined input closed to ground; the nature of the fault is an optional customer selection. Default message is editable.	Warning	Isolate the source of the false signal; check the corresponding customer interface board LED; disconnect the signal lead and reset the control; replace A34 or A32 as indicated.
301	HIGH AC VOLTAGE	Indicates that one or more of the phase voltages has exceeded 130% of nominal, or has exceeded 110% of nominal for 10 seconds.	Shutdown	Set the display to GEN VOLTS L-N and observe; determine if the output voltage the control sees is low or high; isolate to the PCC, alternator, PT/CT module (A36), customer interface board (A34), analog board (A33) or digital board (A32).
303	LOW AC VOLTAGE	Indicates that one or more of the phase voltages has dropped below 85% of nominal for 10 seconds.	Shutdown	Check and repair the PMG or field wiring; check rotating rectifier diodes; check the load and correct any overload; check connectors J8 and J9 on A36, J3 and J5 on A34, and J7 on A37; isolate to A33, A32, A37 or A31.
313	UNDER FREQUENCY	Indicates that engine speed has dropped below 90% of nominal for 10 seconds. Five seconds before shutdown, a Load Dump signal is initiated.	Shutdown	Check Initial Setup (set size); check load and correct any overload; check fuel supply, intake air supply and load; refer to the fault-finding table.
320	OVERCURRENT	Indicates that generator output current has exceeded 110% of rated for 60 seconds.	Warning	Check load and load lead connections.
321	OVERCURRENT	Indicates that generator output current has exceeded 110% of rated, and that a PCC time/current calculation has initiated an overcurrent shutdown.	Shutdown	Check load and load lead connections.
322	SHORT CIRCUIT	Indicates that generator output current has exceeded 175% of rated.	Shutdown	Check load and load lead connections.
330	OVERLOAD	Indicates that three-phase power output exceeds 105% of standby (or 115% of prime) rating. After five seconds, the Load Dump output is activated. After 60 seconds, the OVERLOAD warning is activated.	Warning	Check load and load lead connections.
335	REVERSE POWER	Indicates improper CT or PT phasing (non-parallel units only).	Shutdown	Check CT / PT wiring. Refer to CT Installation in Section 5.
359	FAIL TO START	Engine cranks but fails to start (possible fuel system problem).	Shutdown	Check for empty fuel tank, fuel leaks, or plugged fuel lines; replace dirty fuel filter; replace dirty air filter; reset control and restart.
415	LOW OIL PRESSURE	Engine oil pressure has dropped below the shutdown trip point.	Shutdown	Check oil level, lines and filters; replenish if low; reset control and restart.
421	OIL TEMP	Engine has begun to overheat (oil temperature above unacceptable level) (Optional).	Warning	Reduce load; check air inlets/outlets; if engine can be stopped follow code 151 and check engine oil level.
441	LOW BAT VOLTAGE	Battery voltage supply to the control approaching a low level.	Warning	Check battery charger fuse; recharge or replace battery; clean and tighten cable connections; check engine DC alternator.
442	HIGH BAT VOLTAGE	Battery voltage supply approaching a high level at which control damage can occur.	Warning	Check float level on battery charger; check battery wiring/calibration.
1122	Rated/Idle Trans		Info
1123	SHUTDOWN AFTER BS	A shutdown fault occurred while Battle Short was enabled and transitioned from enabled to disabled.	Shutdown	Review Fault History and perform corrective action.
1124	DELAYED SHUTDOWN	A shutdown fault became active while the Delayed Shutdown feature was enabled.	Warning	Review Fault History and perform corrective action.
1131	BATTLE SHORT ACTIVE	Control is in Battle Short mode (bypasses several critical fault shutdowns).	Warning	None; used for genset operation during emergencies.
1311	Customer Input #1	Configurable customer input 1 fault.	Warning	Check TB1-12; check external wiring; verify fault function settings.
1311, 1312, 1317, 1318	CUSTOMER INPUT #1 - #4	Optional customer-selected fault input is active.		Disconnect signal lead from TB1 and reset the control; check external wiring/active input selection.
1312	Customer Input #2	Configurable customer input 2 fault.	Warning	Check TB1-14; check external wiring; verify fault function settings.
1317	Low Coolant Level	Optional coolant level sensor indicates low coolant level.	Warning	Add coolant; check coolant level sensor connections and operation; verify calibration.
1318	Low Fuel	Optional low fuel level switch indicates low fuel.	Warning	Add fuel; verify switch operation; check wiring; verify settings.
1334	CRIT SCALER OR	Incorrect feature or calibration was entered into control.	Shutdown	Reload correct feature/calibration file.
1335	NONCRIT SCALER OR	Incorrect feature or calibration was entered into control.	Warning	Reload correct feature/calibration file.
1337	No Message		Info
1416	FAIL TO SHUTDOWN	Genset continues to run after receiving shutdown command (Battle Short feature enabled).	Warning	Check Battle Short feature setting.
1417	POWER DOWN ERROR	Controller cannot power down because of an unknown condition.	Warning	Check for possible battery drain.
1433	EMERGENCY STOP	Local Emergency Stop.	Shutdown	Pull the button out; move switch to O; press Fault Acknowledge/Reset; select Manual or Auto.
1434	REMOTE E-STOP	Remote Emergency Stop.	Shutdown	See code 1433 to reset.
1435	LOW COOLANT TEMP	Engine coolant heater is not operating or not circulating coolant (coolant <=70 F [21 C]).	Warning	Check coolant heater power/fuse/cord; check coolant level; check heater element (10 to 60 ohms); check sensor.
1438	FAIL TO CRANK	Engine failed to crank after the PCC received a start signal.	Shutdown	Test for B+ at the starter; check fuse F3 (2 Amps); check K4 start pilot relay and starter circuitry; refer to code 121.
1442	WEAK BATTERY	During cranking battery voltage at or below weak battery trip point.	Warning	Recharge or replace battery; check electrolyte level and connections; check harness.
1443	BATTERY FAILED	Dead battery - engine will not start.	Shutdown	See code 1438 instructions.
1444	KW OVERLOAD	Generator output power exceeded 105% of genset rating (3 sec at 110% of rated).	Warning	Check load and load lead connections; check CTs and CT connections.
1445	SHORT CIRCUIT	Generator output current exceeded 175% of rated.	Shutdown	Check load and load lead connections (fault may not reset for several minutes).
1446	HIGH AC VOLTAGE	Phase voltage exceeded 130% of nominal, or 110% of nominal for 10 seconds.	Shutdown	Check fault simulation; clear fault and restart; refer to Generator/Base Board Isolation Procedure.

Showing the first 80 of 158 codes.

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Procedures

Adjusting Values/Parameters adjustment

⚠ If Home button or Previous Main Menu button is pressed before pressing save symbol, changes are not saved.

Press button next to symbol in display until + and − symbols are displayed.
Press button next to arrow symbols to move to numeric character to change.
Press button next to + symbol to increase value or select parameter.
Press button next to − symbol to decrease value or select parameter.
After adjusting values/selecting parameters, press symbol to save changes.

Day Tank Controller Conversion 240 VAC to 120 VAC adjustment

Remove the two jumpers between terminals TB1-6 and TB1-7 and connect one between TB1-5 and TB1-6 and the other between TB1-7 and TB1-8.
Move selector switch S103 on the control PCB to the up position for 120V.
On the control transformer, remove the two jumpers between terminals H2 and H3 and connect one between H1 and H3 and the other between H2 and H4.

Dip Adjustment adjustment

Turn the DIP pot clockwise to increase the voltage vs frequency slope for frequencies below the UFRO threshold.
Greater slope gives greater voltage roll off as frequency drops, easing large load pickup but increasing voltage dip.
Turn the pot fully counterclockwise to make the slope the same above and below the threshold frequency.

Disabling the AMF Feature adjustment

⚠ Must be performed by a qualified technician.

Tools: InPower service tool

Connect to the PCC 1.1 or PCC 2.3 via InPower.
Navigate to Adjustments->Features->Automatic Transfer Switch folder.
Select the Auto Mains Failure Enable parameter.
Double-click on Enabled in the Value field.
Select Disabled from the pop-up choices.
Select Device->Save Adjustments from the top menu bar.
Click Save on the confirmation pop-up.
Disconnect InPower from the PCC1302 after confirmation.

Dwell Adjustment adjustment

Turn the DWELL pot clockwise to increase dwell time (voltage recovery time when frequency dips below threshold).
Turn the DWELL pot fully counterclockwise to eliminate dwell.
With no dwell, voltage recovery follows engine speed recovery.

Electric Governor Controller Adjustments adjustment

⚠ If adjustment must be made while the unit is running, use extreme caution around hot manifolds and moving parts

Tools: Frequency meter

Move RUN/STOP/REMOTE switch to RUN and operate set at no load.
Confirm DROOP potentiometer adjust is set at zero position.
Set speed by adjusting the SPEED potentiometer to 50 or 60 Hz.
Adjust GAIN potentiometer clockwise until engine starts to hunt, then counterclockwise until speed is stable.
Adjust the 'B' potentiometer the same as GAIN.
Adjust the 'I' potentiometer to decrease overshoot above rated speed.
Apply 1/4 load and adjust the GAIN potentiometer again.
Apply full load to be certain the set will carry it; lengthen actuator linkage if it will not.

Fuel Injection Pump Speed Lever Adjustment adjustment

Make sure the generator set is off and the battery is disconnected.
If replacing pump or engine, discard speed adjust screw and tamper proof wire and seal.
Replace the low idle screw; reuse throttle screw nut and acorn nut.
Pull throttle lever back and screw new low idle screw until it contacts boss.
Continue tightening until throttle lever is locked in place.
Tighten the throttle lock nut.
Install tamper proof wire and seal.
Set the throttle lever as shown and lock it using seal wire.

Fuel Pump Control: Convert 120 VAC to 240 VAC adjustment

Remove jumpers between TB1-5/TB1-6 and TB1-7/TB1-8; connect two jumpers between TB1-6 and TB1-7.
Move selector switch S103 on control PCB to down position for 240 VAC.
If equipped with a transformer, remove jumpers between H1/H3 and H2/H4 and connect two jumpers between H2 and H3.
Attach a tag to the control box indicating the supply voltage.

Fuel Pump Control: Convert 240 VAC to 120 VAC adjustment

Remove jumpers between TB1-6/TB1-7; connect one jumper TB1-5 to TB1-6 and one TB1-7 to TB1-8.
Move selector switch S103 on control PCB to up position for 120V.
If equipped with a transformer, remove jumpers between H2/H3 and connect one between H1-H3 and one between H2-H4.

Governor Adjustments (Type A Electric Governor) adjustment

Set selector switch S1 to OFF, S2 to appropriate model position.
Set pots initially: Gain 20%, I 20%, D 30%, Droop 0%.
Start set, adjust Speed pot for required frequency (60Hz=1800RPM or 50Hz=1500RPM) at operating temperature.
Disconnect load, turn Gain pot to 100% or until unstable, then back off until stable.
Adjust D and I pots similarly; readjust Speed if necessary.
Push throttle to minimum speed, release and observe overshoot (2-5 Hz acceptable); adjust I pot to reduce overshoot or hunting.

Mechanical Governor Adjustment adjustment

Tools: Accurate frequency meter

Using an accurate frequency meter, measure frequency under full load.
Turn the speed adjustment screw on the governor to adjust to nominal 50 or 60 Hz.

Over / Under Voltage Module Recalibration adjustment

Remove the two screws securing the top to the case and withdraw the top assembly.
Adjust the UNDER setpoint SET pot to 75 percent.
Apply single-phase, 60 Hertz, 104.25 VAC across terminals L and N.
Adjust pot R25 on the PC board until the relay trips (de-energizes).
Adjust the OVER setpoint SET pot to 125 percent.
Apply single-phase, 60 Hertz, 173.75 VAC across terminals L and N.
Adjust pot R26 on the PC board until the relay trips (energizes).
Repeat until no adjustments are necessary, then reassemble the module.

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Voltage reconnection

Voltage	Phase	Connection	Leads	Notes
		AVR response jumper	A to C	For generator output 90 kW or less (SX440 and MX321)
		Auxiliary terminal board TB21	K1, K2, P2, P3, P4, S2, S1, A2, A1	A1 and A2 connect a VAR/power factor controller when paralleling with a utility; S1 and S2 connect a droop compensating CT when paralleling with a generator set or utility
		CT1 - U load leads (A phase); CT2 - V load leads (B phase); CT3 - W load leads (C phase)	6 lead gensets: generator output leads routed through CTs; 12 lead gensets: load wires routed through CTs	12-lead sets have dual secondary CTs (3 pins); 6-lead sets have single secondary CTs (2 pins)
		Day tank LO SHUTDOWN engine shutdown connection	TB1-14 to engine block ground; TB1-15 to TB2-16 on the ECM
		Fault relay K8/K9 (Dry Contact Module)	K8=Over Crank, Low Oil Pressure, High Engine Temperature, Low Coolant Level, Low Fuel Level; K9=Low Fuel Level, Rupture Basin	Contact ratings: 40A max carry/break N.O. 12V coil, 30A N.C. 12V coil, 20A N.O./10A N.C. 24V coil
		MX321 PMG-excited jumper positions	2-3, 4-5 and 6-7	These jumpers must be in these positions
		MX321 voltage regulator frequency jumper	3-2 for 50 Hz; 3-1 for 60 Hz
		SX440 voltage regulator frequency jumper	C-50 for 50 Hz; C-60 for 60 Hz
		TB3 (ECM alternative RUN/STOP/REMOTE connection)	TB3-1=REMOTE, TB3-2=RUN, TB3-3=STOP	Provides alternative direct connection to ECM for troubleshooting or customer connection
		Voltage trimmer R21	voltage regulator terminals 1 and 2	There must be a jumper between terminals 1 and 2 when voltage trimmer R21 is not used
	single phase	QSG-Series power distribution panel voltage selector switch S1 position	main output terminals	Rotary switch under lockable cover selects 120/240 VAC single phase
	single phase	Voltage regulator terminal 6	jumpered to terminal 8	When the generator is connected for single-phase output, terminal 6 is not connected to the isolation transformer
	three phase	QSG-Series power distribution panel voltage selector switch S1 position	main output terminals	Rotary switch selects 120/208 VAC three phase
110V - 120V L-N	Single phase, 2-wire	Jumper locations for single phase, 2-wire		PTC Module AC wiring (0300-5382-01, -02)
120	single phase	Day tank fuel pump control power reconnection	move jumpers from TB1-6/TB1-7 to TB1-5/TB1-6 and TB1-7/TB1-8	Move selector switch S103 on the control PCB to the up position for 120 V (factory set for 240 V, S103 down)
120/208 thru 139/240	three phase	Broad range	12	150 deg C rise rating 230 kW / 288 kVA per ADS-212
120/240	single phase	Double delta	4	125 deg C rise rating 175/219 kW/kVA; 105 deg C rise rating 157/196 kW/kVA
190, 200, 208, 220, 230, 240, 380, 416, 440, 460, 600 (L-L)	3 (three phase)	3 or 4 wires		Voltage Configuration submenu; default = 3Ph 208V 4W
190V - 240V L-L	Three phase	Jumper locations for three phase, 190V-240V L-L		Use 0300-5382-01 for 190V-240V L-L, 50/60 Hz
200, 220, 230, 240 (L-L)	1 (single phase)	3 wires		Voltage Configuration submenu (Governor/Regulator Setup)
200V - 240V L-L	Single phase, 3-wire	Jumper locations for single phase, 3-wire		PTC Module AC wiring
24		Day tank fuel pump control logic power (two lead harness, no transformer)	TB1-19 to positive (+) 24 V starter motor solenoid; TB-20 to negative (-)	Provides 24 VDC for the control circuit
240	single phase	Day tank fuel pump control default factory connection	jumpers between terminals TB1-6 and TB1-7	Selector switch S103 on the control PCB in the down position for 240 V
240/416 thru 277/480	three phase	Broad range	12	150 deg C rise rating 255 kW / 319 kVA
347/600	three phase	Upper broad range (LBR)	6	150 deg C rise rating 230 kW / 288 kVA; lower broad range 110/190 thru 120/208, 220/380 thru 240/416
380V - 600V L-L	Three phase	Jumper locations for three phase, 380V-600V L-L		Use 0300-5382-02 for 380V-600V L-L, 50/60 Hz

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Parts cataloged across the Cummins/Onan 4BT3.9 family

149

Part #	Description	Category
982-0200	Air Filter	Air filter
309-0272	Regulator, Voltage - 24 VDC (Used on 35 A MP Alternator)	Alternator
309-0561	Alternator & Drive Components Group Pulley. Alternator - Multi Groove (Use with 35 A MP Alternator)	Alternator
AN500T0083	ALTERNATOR	Alternator
150-2007	Guard. Belt Screw. Cap - Hex Head (1/2-13 X 2-1/4“)	Belt
187-0008	Belt, Drive	Belt
187-0009	Belt, Drive	Belt
328876800	Belt, V-Grooved	Belt
FP-3034946	Multi-Groove Fan Belts (Ribbed 8) (62.5" X 1.125")	Belt
FP-3911558	Belt, V Ribbed (Alternator)	Belt
187-0011	Filter, Fuel	Fuel filter
3824469	fuel pump gear puller	Fuel pump
102-1147	Gasket, Drain-Oil Pan	Gasket
187-0002	Gasket Kit, End - Top	Gasket
DM-3801371	Gasket Set - 4BT 3.9	Gasket
FP-3901356	Turbo Charger Mounting Gasket	Gasket
FP-3905443	Gasket, Exhaust Manifold	Gasket
FP-3911535	Gasket, Oil Pan	Gasket
FP-3926760	Gasket, Oil Cooler Core	Gasket
FP-3928493	Gasket, Rear Cover	Gasket
FP-3929792	Gasket, Filter Head	Gasket
FP-3937706	Turbocharger Oil Drain Gasket (H x 35)	Gasket
FP-3938157	Gasket, Pick-Up Tube	Gasket
FP-3938158	Gasket, Air Intake Connection	Gasket
FP-3939258	Gasket, Fuel Transfer Pump Mounting	Gasket
FP-4B39PREM	4B/4BT3.9 In-Frame Kit w/upper gasket set & oil pan gasket	Gasket
FP-4B39PREML	4B/4BT3.9 In-Frame Kit w/upper gasket set & oil pan gasket (late)	Gasket
FP-IFK4B39PREM	4B/4BT3.9 In-Frame Kit w/upper gasket set & oil pan gasket	Gasket
FP-IFK4B39PREML	4B/4BT3.9 In-Frame Kit w/upper gasket set & oil pan gasket (late)	Gasket
501-0441	Line, Fuel - Flex (Fuel In)	Hose
501-0502	Line, Fuel-Flex (Fuel Out)	Hose
503-0098	Hose, Oil Drain - Bulk (Order By The Foot - 3 Feet Required)	Hose
503-0183	Clamp, Hose	Hose
503-0197	Clip, Hose	Hose
503-0685	Clamp, Hose	Hose
DM-3805455	Oil Cooler Hose - 4BT 3.9	Hose
3822509	Injection Pump Bore Brush Service Tool	Injector
3823276	injector bore brush	Injector
DM-3029550	Fuel Injector - 4BT 3.9	Injector
0332-3925-02	Jumper-Terminal	Jumper terminal
0332-3943-02	Jumper-Terminal	Jumper terminal
REC149-2106	By-pass filter I	Oil filter
REC1491754	By-pass filter II	Oil filter
0249-0814	Relay 2P Base	Service part / kit
0332-3926	Terminal Block (End Stop)	Service part / kit
0332-3927-02	Terminal Block (End Plate)	Service part / kit
102-1237	Adapter, Drain-Oil	Service part / kit
151-0611	Control, Governor	Service part / kit
155-2175	Clamp, Muffler 4"	Service part / kit
187-0007	INJ	Service part / kit
187-0012	Filter, Fuel	Service part / kit
187-0015	Filter, Oil	Service part / kit
201-3434-01	Diode, Positive (Forward) Includes Lead	Service part / kit
201-3434-02	Diode, Negative (Reverse) Includes Lead	Service part / kit
300-2810	Board - Engine Monitor (All) (Includes Fuses)	Service part / kit
305-0823	# Model MX321	Service part / kit
309-0553	Switch, Temperature-Pre Water	Service part / kit
309-0554	SWITCH WATER	Service part / kit
323-1200	# Socket, Contact (Used in J1, J2)	Service part / kit
323-1304	tiotming, Umector	Service part / kit
323-1306	Genset component (SJB series)	Service part / kit
332-0051	Clamp, Loop	Service part / kit
332-0941	*Tie, Cable	Service part / kit
332-1279	Terminal. Lug - Ring (3/8	Service part / kit
332-1445	Tie, Cable 18 98-5219 1 Decal - Panel Front (Not I l l u s t r a t e d ) 19 98-5220 1 Decal	Service part / kit
332-2739	Bracket	Service part / kit
332-2921	Switch, Temperature - Washer, Lock (M8)	Service part / kit
3377259	bosch timing tool (ve)	Service part / kit
357-0030	Rectifier	Service part / kit
416-0446	Cable, Battery - Jumper	Service part / kit
504-0011	Valve, Shutoff (1/2”)	Service part / kit
505-0026	Coupling, Pipe (1/8")	Service part / kit
505-0050	Elbow, Street (1/2' x 90 ° )	Service part / kit
505-0098	Band	Service part / kit
505-0104	Nipple, Pipe - Close	Service part / kit
505-0185	Nipple, Half (1/2' x 1.5' lg)	Service part / kit
526-0008	148-036’?	Service part / kit
526-0018	Gasket, Flange (1-3/4)	Service part / kit
526-0115	Washer (5/16 “)	Service part / kit
526-0196	Washer, Spacer - Shield JC)INT, BALL LINKAGE	Service part / kit
526-0327	Control, Governor	Service part / kit
800-0012	Screw, Cap - Hex Head (1/4-20 x 2-1/4”) Begin Spec C MANIFOLD KIT, INTAKE	Service part / kit
800-2060	Screw, Cap - Hex Head (M8x 1.25 x35)	Service part / kit
800-2110	Hood, Inlet - Air Molded	Service part / kit
800-2112	Screw. Cap - Hex Head (M12 x 30nin)	Service part / kit
812-0075	Screw-RHM(8-32xl/4)	Service part / kit
813-0103	Screw, Machine - Round Head (#10-32 x 3/4º)	Service part / kit
815-0172	Cover, Adapter Outlet	Service part / kit
850-0025	Screw, Machine - Round Head (#8-32 x 3/8" )	Service part / kit
850-0030	Washer, Lock - Spring (#10)	Service part / kit
850-0050	Washer, Lock - Spring (3/8”)	Service part / kit
850-2006	Washer, Lock - Spring (M6)	Service part / kit
850-2008	Washer, Lock (M8)	Service part / kit
850-2012	Washer, Lock - Spring (M12)	Service part / kit
856-0013	Washer, Lock - W/EIT (1/2)	Service part / kit
860-2007	Circuit Breaker Used With Westinghouse Circuit Breaker	Service part / kit
870-0053	Nut, Hex (s10-32)	Service part / kit
870-0131	Nut. Hex - with ET (#10-32)	Service part / kit
870-0212	Nut, Locking (1/4-20)	Service part / kit
871-0010	Nut, Hex - Srass (#10-32) Washer, Lock - EIT (#10) Washer, Lock - IT (#10)	Service part / kit
871-0028	NUT	Service part / kit
960-0136	Battery, 24V, 55Ah, AGM	Service part / kit
965-0520	Cooling Fan	Service part / kit
DM-3802010	Main Bearing Set Standard - 4BT 3.9, 6BT 5.9, 6CT 8.3	Service part / kit
FP-3903575	Kit, Solenoid 12 Volt	Service part / kit
FP-3903576	Kit, Solenoid 24 Volt	Service part / kit
FP-3910739	Bearing, Ball (Fan Drive)	Service part / kit
FP-3918428	Plunger, Pressure Regulator	Service part / kit
FP-3957543	Element, Oil Cooler	Service part / kit
187-0001	Pump, Water	Pump
187-0013	Pump, Transfer-Fuel	Pump
187-0018	INJ. PUMP	Pump
DM-3004242	Fuel Transfer Pump - 4BT 3.9	Pump
DM-3805403	Water Pump - 4BT 3.9, 6BT 5.9	Pump
DM-3807788	Oil Pump - 4BT 3.9	Pump
FP-3286277	Water Pump	Pump
FP-3928143	Pump, Fuel Transfer	Pump
FP-3970880	Pump, Fuel Transfer	Pump
FP-4939585	Pump, Lubricating Oil	Pump
FP-4947710	Pump, Fuel Transfer	Pump
0307-3047	Relay (24V)	Relay 24v
509-0266-01	Ring, O	Seal
FP-3883284	Seal, O-Ring, Air Intake Connection	Seal
FP-3900808	Seal, Injector	Seal
FP-3903380	Seal, Banjo Connector (Fuel Manifold)	Seal
FP-3906659	Seal, Injector	Seal
FP-3906698	Seal, Rectangular Ring	Seal
FP-3909356	Seal, Injector	Seal
FP-3909397	Seal, O-Ring	Seal
FP-3909410	Seal, Rear Service Kit (Dry Clutch Housing)	Seal
FP-3913994	Seal, O-Ring	Seal
FP-3921640	Seal, Valve Stem (Intake & Exhaust) (For Engines Built Before April 2003)	Seal
FP-3931824	Seal, O-Ring, Turbo Oil Line	Seal
FP-3937111	Seal, Front Service Kit	Seal
FP-3957912	Seal, Valve Stem (For Engines Built After April 2003)	Seal
150-2201	Sensor, Speed – Magnetic	Sensor
193-0244	Sender, Oil Pressure (E1)	Sensor
193-0353	Sender, Temperature - Oil	Sensor
193-0375	Sender, Coolant	Sensor
309-0269	Sender, Temperature-Lo Engine	Sensor
505-0059	Sensor, Water Pressure	Sensor
M-1695	Oil temperature sender	Sensor
AN500T0013	STARTER MOTOR	Starter
0332-3923-02	Terminal Block	Terminal block
0332-4036-02	Terminal Block (Earth)	Terminal block
187-0020	Thermostat	Thermostat
DM-3015282	Thermostat 180F - 4BT 3.9, 6BT 5.9	Thermostat
FP-3802273	Kit, Thermostat (83° C), (181° F)	Thermostat
FP-3917324	Assembly, Thermostat (83° C), (181° F)	Thermostat

Parts cataloged across all variants of this engine family — verify the exact part fits your specific variant and serial number before ordering.

Common questions

What is the oil capacity of the Cummins/Onan 4BT3.9-G4?

The Cummins/Onan 4BT3.9-G4 engine has an oil capacity of 10.9 liters.

What is the displacement of the Cummins/Onan 4BT3.9-G4?

The Cummins/Onan 4BT3.9-G4 has a displacement of 3.9 liters with 4 cylinders.

Which generators use the Cummins/Onan 4BT3.9-G4 engine?

The Cummins/Onan 4BT3.9-G4 powers 11 generator set(s), including Cummins/Onan 40DGCA, Cummins/Onan 42DGCG, Cummins/Onan 50 DGCA, Cummins/Onan 50DGCB, Cummins/Onan 51DGCH.

How often should you change the oil in the Cummins/Onan 4BT3.9-G4?

The Cummins/Onan 4BT3.9-G4 oil change interval is every 1000 hours.

What is a common problem with the Cummins/Onan 4BT3.9-G4 engine?

A commonly reported issue on generators using the Cummins/Onan 4BT3.9-G4 is: The FAULT 1 or FAULT 2 fault lamp lights. Engine shuts down immediately, engine runs for several seconds and then shuts down, or engine continues to run. Cause: The standard undesignated fault functions are programmed to shut down the set when a fault is sensed. Fault 1 is time delayed while Fault 2 is immediate. The nature of the fault is an optional selection that is determined when the set installation is designed. The undesignated fault functions may also be programmed for non-shutdown or non-time delay.