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Cummins/Onan 4B3.3 G1 Engine

The Cummins/Onan 4B3.3 G1 is an engine. It powers generator sets from Cummins/Onan, including the C38 D5.

Also known as: Cummins Inc. 4B3.3 G1

Part of the Cummins/Onan 4B3.3 engine family — 2 variants share parts & fitment.

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

Engine specifications

Generator sets powered by this engine

Cummins/Onan C38 D5

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

Common problems

LOW ACE VOLTAGE (SHUTDOWN) — Engine will shut down 13
Cause: Fault simulation was enabled with a PC based service tool
Fix: With a PC based service tool, verify that the related fault simulation is not enabled. If you do not have a PC based service tool, remove battery power from the control to disable fault simulation overrides.
Engine does not crank in manual mode (no fault message) — Engine will not start
Cause: No power supplied to control; Poor battery cable connections
Fix: Clean the battery cable terminals and tighten all connections; Remove connector P11 and check for B+ at P11-3 & 15 and GND at P11-9 & 10. If B+ or ground missing, isolate to harness and TB BAT terminal mounted on engine block. If B+ and ground check OK, cycle power to base board by reconnecting P11 and retry operation.
LOW OIL OR PRE-LOW PRESSURE (WARNING/SHUTDOWN) OIL PRESSURE SENSOR TYPE : SENDER — Calibration-dependent. No action is taken by the Control for code 215. Engine will shut down for code 2 2/215
Cause: Fault simulation was enabled with a PC based service tool
Fix: With a PC based service tool, verify that the fault simulation is not enabled for the oil pressure sensor. If you do not have a PC based service tool, remove battery power from the control to disable fault simulation overrides.
HIGH AC VOLTAGE (SHUTDOWN) — Engine will shut down 12
Cause: Fault simulation was enabled with a PC based service tool
Fix: With a PC based service tool, verify that the related fault simulation is not enabled. If you do not have a PC based service tool, remove battery power from the control to disable fault simulation overrides.
HIGH OR PRE-HIGH COOLANT TEMPERATURE (SHUTDOWN/SHUTDOWN) — Calibration-dependent. No action is taken by the Control for code 202. Engine will shut down for code 1 1/202
Cause: Fault simulation was enabled with a PC based service tool
Fix: With a PC based service tool, verify that the fault simulation is not enabled for the coolant sensor. If you do not have a PC based service tool, remove battery power from the control to disable fault simulation overrides.
Generator set output frequency cannot be maintained. 81 u
Engine does not crank in remote mode (no fault message) — Engine will not start in remote mode, but starts in manual mode
Cause: The remote start switch or configurable wiring is faulty
Fix: Reset the control. Attempt to start, and check for ground at TB1-11. If ground level is not present, isolate to the remote switch or configurable wiring. Repair as necessary. If ground is present, go to next step.
Configurable Input (Warning) — Warning. 204/205
Cause: If there is no actual fault, the problem may be an external wiring problem
Fix: Disconnect the signal lead from TB1 and reset the control. Check the following pins. CUST_IN1 - TB1-14 CUST_IN2 - TB1-12 If the message drops out, the external wiring has a short circuit. Grounding of either input activates fault
WEAK BATTERY — Lamp: Warning; Indicates that during cranking, the battery voltage is at or below the weak battery warning trip point for a time greater than or equal to the weak battery set time 221
Fix: See code 213 for corrective action.
Weak Battery (Warning) 221
Cause: Refer to code 213
Fix: Refer to code 213
Voltage on any phase has dropped below a preset value.
Fix: Adjustable over a range of 50-95% of voltage, time delay 2-20 seconds. Default value is 90% for 5 seconds.
VOLTAGE BIAS OOR — Lamp: Shutdown; Indicates the voltage bias circuit output is out of range (OOR), high or low. (I/O Module option.) 102
UNDER FREQUENCY — Lamp: Shutdown; Indicates that engine speed has dropped below 90% of nominal for approximately 10 seconds 15
Fix: Check fuel supply, intake air supply and load.
Under Frequency (Shutdown) — Generator set will shut down. 15
Cause: Fault threshold is not set correctly with PC based service tool; Overload; Fuel or air delivery problem; Governor fault; Loose connector or Base board is bad
Fix: Reset the threshold to the lowest allowable setting. Determine the required operating range before adjusting the threshold; Check the load and correct any overload. Check operation by disconnecting load and restarting generator set; Refer to the engine service manual; Check fuel shutoff solenoid adjustment; Repair connections (P13) or replace the Base board if necessary
SPEED SIGNAL LOST — Lamp: Shutdown; Indicates that no magnetic pickup pulses are sensed for a Loss of Speed delay. If a magnetic pickup is not installed, then speed sensing is performed by monitoring AC line frequency, this fault cannot occur 45

Compiled from service & troubleshooting documentation across every generator set that uses the Cummins/Onan 4B3.3 G1.

Service specifications

Type	Item	Value	Unit	Condition
Resistance	Coolant heater coil resistance	10 to 60	ohms	closed heater
Resistance	Injection pump actuator resistance	2.3	ohms
Resistance	Main rotor resistance	0.415	Ohms	within 10% of value
Resistance	Main rotor resistance	0.437	Ohms	within 10% of value
Resistance	Main rotor resistance	0.465	Ohms	within 10% of value
Resistance	Main rotor resistance	0.545	Ohms	within 10% of value
Resistance	Main rotor resistance	0.551	Ohms	within 10% of value
Resistance	Main rotor resistance	0.657	Ohms	within 10% of value
Resistance	Main rotor resistance	0.67	Ohms	within 10% of value
Resistance	Main rotor resistance	0.708	Ohms	within 10% of value
Resistance	Main rotor resistance	0.857	Ohms	within 10% of value
Resistance	Main rotor resistance	0.89	Ohms	within 10% of value
Resistance	Main rotor resistance	0.983	Ohms	within 10% of value
Resistance	Main rotor resistance	0.99	Ohms	within 10% of value
Resistance	Main stator winding resistance	0.3	Ohms
Resistance	Main stator winding resistance	0.353	Ohms
Resistance	Main stator winding resistance	0.51	Ohms
Resistance	Main stator winding resistance	0.625	Ohms
Resistance	Main stator winding resistance	0.95	Ohms
Resistance	Main stator winding resistance	1.33	Ohms
Resistance	Main stator winding resistance	1.908	Ohms
Resistance	Stator insulation resistance	1.0	Meg-Ohm	minimum to Earth (Ground)
Torque	AVR cover to NDE bracket	5	Nm
Torque	AVR to NDE bracket	5	Nm
Torque	Axial air inlet cover to NDE bracket	5	Nm
Torque	Clamping spacer to rectifier hub	2.8/3.6	Nm
Torque	Coupling disc to flywheel	51	Nm
Torque	Coupling disc to shaft	75	Nm
Torque	DE Adaptor to Flywheel housing	51	Nm
Torque	DE Adaptor to frame blocks	26	Nm
Torque	DE Air outlet cover	6.5	Nm
Torque	Diode fitting	2.8/3.6	Nm
Torque	Diode fitting torque	36 to 42	in-lbs (4 to 4.8 Nm)
Torque	EBG Housing cover to housing	6.5	Nm
Torque	EBG Rtr to shaft	50	Nm
Torque	EBG Str Hsg to NDE bracket	10	Nm
Torque	EBG Str to EBG Str Hsg	10	Nm
Torque	Earth lead to NDE bracket	6	Nm
Torque	Excitor stator to NDE bracket	10	Nm
Torque	Fan to fan hub 290 and 344	5	Nm
Torque	Main rotor terminals	24	in-lbs (2.7 Nm)
Torque	NDE bracket to Frame blocks	26	Nm
Torque	Pigtail terminals	24	in-lbs (2.7 Nm)
Torque	Radial Inlet cover to Nde bracket	5	Nm
Torque	Rectifier hub to excitor rotor	2.8/3.6	Nm
Torque	Rotor leads to Clamping spacer	2.8/3.6	Nm
Torque	Small Terminal box to NDE bracket	5	Nm
Torque	Stator Lead to terminal studs	6.5	Nm
Torque	Surge suppresser terminals	24	in-lbs (2.7 Nm)
Torque	Terminal block to NDE bracket	5	Nm
Torque	Terminal box lid to terminal box	5	Nm
Torque	Varistor to rectifier hub	2.8/3.6	Nm
Voltage	MPU output while cranking	3.5 to 15	VAC	while cranking
Voltage	Oil pressure sender output	0.5	VDC	at 0 psi
Voltage	Oil pressure sender output	4.5	VDC	at 100 psi

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
Fuel	Number 2 diesel fuel				Direct injection

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
1	HIGH COOLANT TEMP	Engine has overheated; coolant temperature has risen above shutdown trip point.	Shutdown	Allow engine to cool. Check coolant level, airflow obstructions, fan belt, blower and circulation pumps. Reset and restart.
2	LOW OIL PRESSURE	Engine oil pressure has dropped below shutdown trip point.	Shutdown	Check oil level, lines and filters; replenish if low; reset and restart; check oil switch.
12	HIGH AC VOLTAGE	One or more phase voltages exceeded 130% of nominal for 0 second, or exceeded high AC voltage threshold for time delay.	Shutdown	Check fault simulation, block load removal, threshold setting, Base board or generator, voltage sense connections.
13	LOW AC VOLTAGE	One or more phase voltages dropped below low AC voltage threshold for time delay.	Shutdown	Check fault simulation, threshold, overload, output connections, excitation inputs, rotating rectifier diodes, connector or Base board.
14	OVER FREQUENCY	Frequency is 10% above base frequency for approximately 10 seconds.	Shutdown	Check threshold, fuel or air delivery, governor, connector or Base board.
15	UNDER FREQUENCY	Engine speed dropped below 90% of nominal for approximately 10 seconds.	Shutdown	Check fuel supply, intake air supply, load, threshold, governor, connector or Base board.
27	EXCITATION FAULT	Loss of all three voltage sense leads or failure in excitation circuit.	Shutdown	Check field wiring (X1 and X2) for shorts or opens.
31	OVERSPEED	Engine exceeded normal operating speed; default thresholds 1725 RPM (50 Hz) or 2075 RPM (60 Hz).	Shutdown	Check cold engine, single step large block load removal, fault simulation, threshold, MPU, governor, flywheel teeth, fuel stop settings.
38	FIELD OVERLOAD	Field AVR Duty Cycle has been at maximum for at least 15 seconds.	Shutdown
45	SPEED SIGNAL LOST	No magnetic pickup pulses are sensed for Loss of Speed delay; if no MPU, speed sensing is by AC line frequency and fault cannot occur.	Shutdown	Inspect MPU wires/connector pins; test MPU for 3.5 to 15 VAC while cranking; check P11-12 to P11-24; replace Base board if needed.
46	HIGH AC CURRENT	Individual phase alternator output current exceeded high current threshold continuously for more than time delay.	Shutdown	Check load and load lead connections.
61	EMERGENCY STOP	Remote Emergency Stop.	Shutdown	Open (disable) remote emergency stop button; move rocker switch to OFF or press OFF; select desired operating mode.
71	SPEED HZ MATCH	Measured speed and measured AC output frequency do not agree.	Shutdown	Check genset setup for number of flywheel teeth.
72	FAIL TO CRANK	Genset failed to sense rotation for two start attempts; possible control, speed sensing or starting system fault.	Shutdown	Check starter, K7 starter relay, Emergency Stop switch/wiring, MPU circuit or Base board.
73	FAIL TO START	Engine cranks but fails to start; possible fuel system or air induction problem.	Shutdown	Check fuel tank, leaks, plugged fuel lines, fuel filter, air filter; reset and restart; check glow plugs and governor linkage.
74	FAIL TO STOP	Genset continues to run after receiving shutdown command from controller.	Shutdown
75,76	CONFIGURABLE INPUT #1 & #2	Optional configurable input fault.	Shutdown	Disconnect signal lead from TB1 and reset control; check CUST_IN1 TB1-14 and CUST_IN2 TB1-12.
77	SHUTDOWN AFTER BS	A shutdown fault occurred while Battle Short mode was enabled.	Shutdown	Check fault history for faults that may have been bypassed.
81,82,83	ANNUNCIATOR FAULT 1,2,3	Optional configurable annunciator fault.	Shutdown
121	Speed Signal Lost - Shutdown		Shutdown
135/141	Oil Pressure Sensor OOR - Warning		Warning
143	Pre-Low Oil Pressure - Warning		Warning
145	Coolant Sensor OOR - Warning		Warning
146	Pre-High Coolant Temp - Warning		Warning
151	High Coolant Temp - Shutdown		Shutdown
202	PRE-HIGH COOL TMP	Engine is operating near cooling system capacity.	Warning	Review code 1 correction list.
203	LOW COOLANT TEMP	Engine coolant temperature is 70F (21C) or lower.	Warning	Check coolant heater power, low coolant level, heater element; check current draw.
204,205	CONFIGURABLE INPUT #1,#2	Optional configurable input warning.	Warning	Disconnect signal lead from TB1 and reset control; check CUST_IN1 TB1-14 and CUST_IN2 TB1-12.
212	COOL SENSOR OOR	Coolant temperature sensor output is out of range (high or low).	Warning	Check sender, connectors and wires.
213	LOW BATTERY	Battery voltage supply to control is approaching a low level.	Warning	Check battery charger fuse; recharge or replace battery; clean connections; check wiring/calibration, engine DC alternator, float level.
214	HIGH BATTERY	Battery voltage supply to control is approaching a high level.	Warning	Check float level on battery charger; check battery wiring/calibration.
215	PRE-LOW OIL PRESSURE	Engine oil pressure dropped below warning trip point.	Warning	Follow code 2 procedure.
216	HIGH AC CURRENT	One or more phase currents exceeded high AC warning threshold for time delay.	Warning	Check load and load lead connections.
217	OIL PRESS SENSOR OOR	Engine oil pressure sensor output is out of range (high or low).	Warning	Check sender, connectors and wires.
218	BATTLE SHORT ACTIVE	Control is in Battle Short mode; bypasses several fault shutdowns for emergency operation.	Warning
219	CHARGER FAILURE	Battery charging alternator has not reached acceptable voltage range within selected period (default 120 seconds).	Warning	Refer to engine service manual if fault occurs; check wiring if not failed.
220	FAIL TO SHUTDOWN	Genset continues to run after shutdown command; Battle Short feature enabled.	Warning
221	WEAK BATTERY	During cranking, battery voltage is at or below weak battery warning trip point for time >= weak battery set time.	Warning	See code 213 for corrective action.
222,223,224	ANNUNCIATOR FAULT 1,2,3	Optional configurable annunciator fault.	Warning
225	ANNUNCIATOR OUTPUT CONFIGURATION ERROR	Mismatch in configuration of one of the annunciator relay outputs.	Warning	Check network setup for duplicate use of same annunciator relay output; troubleshoot network devices.
234	Overspeed - Shutdown		Shutdown
359	Fail to Start - Shutdown		Shutdown
415	Low Oil Pressure - Shutdown		Shutdown
441	Low Battery - Warning		Warning
442	High Battery - Warning		Warning
1311	CUST_FAULT #1 - Warning		Warning
1312	CUST_FAULT #2 - Warning		Warning
1317	CUST_FAULT #3 - Warning		Warning
1438	Fail to Crank - Shutdown		Shutdown
1442	Weak Battery - Warning		Warning
1446	High AC Voltage - Shutdown		Shutdown
1447	Low AC Voltage - Shutdown		Shutdown
1448	Under Frequency - Shutdown		Shutdown
1449	Over Frequency - Shutdown		Shutdown
1471	High AC Current - Warning		Warning
1472	High AC Current - Shutdown		Shutdown
1944	Annunciator Error - Warning		Warning
2335	Excitation Fault - Shutdown		Shutdown
2677	Fail to Stop - Shutdown		Shutdown

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

Procedures

Valves - Adjust, All adjustment

Disconnect battery cables
Remove valve cover
Adjust valve lash
Test run unit

Generator/Base Board Isolation Procedure diagnostic

⚠ Hazardous voltage

⚠ Test involves unregulated excitation; disconnect loads

Tools: 12 volt battery, Jumper leads, Voltmeter

Throw line circuit breaker OFF and shutdown set.
Disconnect X and XX exciter stator leads from AC harness.
Prepare to measure output voltage across generator terminals.
Bring two jumpers from 12V battery to X (Field +) and XX (Field -).
Check polarity; correct or test inconclusive.
Start set and connect battery negative to XX.
If rated output voltage or higher and balanced, generator OK; troubleshoot control.
If unbalanced, troubleshoot main stator; if uniformly low, troubleshoot exciter and field.

Testing Diodes diagnostic

⚠ Layers of dust can cause diodes to overheat and fail.

Tools: Ohmmeter

Disconnect diode pigtails from terminal posts.
Measure resistance between each diode pigtail and its plate.
Reverse meter probes and repeat.
Replace diode if resistance high or low in both directions.

Testing Exciter Rotor diagnostic

Tools: Wheatstone bridge, Ohmmeter

Disconnect six rotor winding leads from rectifier terminal posts.
Measure resistance across each pair of rotor windings U-V, V-W, W-U.
Replace whole rotor shaft assembly if any winding resistance not per Table 6-1.
Measure insulation resistance between winding lead and rotor laminations.
Replace rotor shaft assembly if insulation resistance less than 1 megohm.

Testing Exciter Stator diagnostic

Tools: Wheatstone bridge, Digital ohmmeter, Insulation resistance meter

Measure winding resistance with Wheatstone bridge or digital ohmmeter.
Replace stator if resistance not as specified in Table 6-1.
Disconnect X and XX leads and isolate from ground.
Measure resistance between either lead and stator laminations.
Replace stator if insulation resistance less than 1 megohm.

Testing Main Rotor diagnostic

Tools: Wheatstone bridge, Digital ohmmeter, Torque wrench

Disconnect two main rotor leads from rotating rectifier terminals.
Measure resistance between two leads with Wheatstone bridge or digital ohmmeter.
Replace rotor if resistance not as specified in Table 6-1.
Measure resistance between either lead and main rotor laminations.
Replace rotor if insulation resistance less than 1 megohm.
Torque terminals to 24 in-lbs (2.7 Nm) when reassembling.

Testing Main Stator diagnostic

Tools: Wheatstone bridge, Insulation tester

Measure resistance across each pair of stator leads U1-U2, U5-U6, V1-V2, V5-V6, W1-W2, W5-W6.
Use Wheatstone bridge or ohmmeter with at least 0.001 ohm precision.
Replace stator if any winding resistance not as specified in Table 6-1.
Disconnect AVR completely before insulation test.
Disconnect Neutral to Earth and any connections.
Use 500 or 1000 V insulation tester for low voltage generators up to 690V.
Minimum insulation value is 1.0 Meg-Ohm to Earth; dry windings if below.

Genset, Standby - Remove and Install installation

Disconnect and connect battery cables
Disconnect and connect output leads
Disconnect and connect fuel lines
Disconnect and connect exhaust system
Remove and install genset
Test run unit

Magnetic Speed Pickup Unit (MPU) Installation installation

⚠ Do not use fan blade to bar over engine.

Tools: MPU sensor, Lock nut

Bar engine until a flywheel gear tooth lines up in center of mounting hole.
Thread sensor in gently by hand until it just touches gear tooth.
Back it out one quarter turn and set lock nut.

Air Cleaner Element - Replace maintenance

Remove and install cover and gasket
Remove and install filter element
Test run unit

Circuit Board Removal/Replacement maintenance

⚠ Electrostatic discharge will damage circuit boards.

Tools: Grounding wrist strap, InPower Service Tool, PCC1301 Interface Kit

Turn off AC power to battery charger.
Remove negative battery cable from starting battery.
Wear grounding wrist strap; attach clip to chassis ground.
Create capture file of genset parameters using InPower before replacing Base board.
Remove circuit board connectors and board.
After replacement, write previous settings to new Base board using capture file.

Fuel Filter, Spin-on Type - Replace maintenance

Remove and install fuel filter
Prime fuel system
Test run unit

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
above 300 volts L-L		X1 & X2	CT secondaries	CTs have dual secondaries (3 pins marked X1, X2 & X3).
below 300 volts L-L		X1 & X3	CT secondaries	CTs have dual secondaries (3 pins marked X1, X2 & X3).

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 4B3.3 family

Part #	Description	Category
AN500T0119	ALTERNATOR	Alternator
0502-1507	Adapter-Hose (Oil)	Hose
0100-3922	Engine-B3.3G1	Service part / kit
0155-4215	Guard-Exhaust (Support)	Service part / kit
0155-4311-02	Guard-Exhaust	Service part / kit
0320-1981-01	Accessories-CB (SD Contact)	Service part / kit
0320-1981-02	Accessories-CB (Shunt Trip)	Service part / kit
0320-2225-01	Accessories-CB (Shunt Trip)	Service part / kit
0320-2225-02	Accessories-CB (SD Contact)	Service part / kit
0331-0618-02	Locknut Conduit	Service part / kit
0332-4001-01	Rail-Terminal Block (300mm)	Service part / kit
0337-3583-04	Strap-Ground	Service part / kit
0338-4487	Harness-Engine (Mechanical governor)	Service part / kit
0338-4720	Harness-Engine (Electronic governor)	Service part / kit
0338-4819-02	Harness AC	Service part / kit
0338-4819-03	Harness AC	Service part / kit
0504-0264-01	Valve-Hydraulic (Oil)	Service part / kit
0505-0019	Bushing-Reducer	Service part / kit
0505-2235	Adaptor-Pipe	Service part / kit
0526-0399-56	Washer-Flat (M5)	Service part / kit
0526-0399-60	Washer-Flat (M8)	Service part / kit
0526-0399-62	Washer-Flat (M10)	Service part / kit
0800-0309-93	Screw-Hex Head (M5)	Service part / kit
0800-3017-19	Screw-Hex Head (M8 X 20)	Service part / kit
0800-3017-35	Screw HHC (M10)	Service part / kit
0800-3017-37	Screw-Hex Head (M10 X 25)	Service part / kit
0850-0114-52	Washer-Lock (M5)	Service part / kit
0850-0114-54	Washer-Lock (M8)	Service part / kit
0850-0114-55	Washer-Lock (M10)	Service part / kit
0862-0026-55	Nut-Hex (M8)	Service part / kit
0862-0026-56	Nut-Hex (M10)	Service part / kit
0872-0020-01	Standoff	Service part / kit
0872-0021	Standoff	Service part / kit
432PSV6551	Selector Switch	Service part / kit
961-0518	(Issue1)	Service part / kit
0193-0430-01	Sender-Pressure	Sensor
A-345052	Engine oxygen sensor	Sensor
GM28980	UEGO Oxygen Sensor	Sensor
25164640	SPARK PLUG,(*33,35 )(AC- R45TS)(AC-DELCO #2)	Spark plug
0193-0432	Thermostat	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

Which generators use the Cummins/Onan 4B3.3 G1 engine?

The Cummins/Onan 4B3.3 G1 powers 1 generator set(s), including Cummins/Onan C38 D5.

What is a common problem with the Cummins/Onan 4B3.3 G1 engine?

A commonly reported issue on generators using the Cummins/Onan 4B3.3 G1 is: LOW ACE VOLTAGE (SHUTDOWN) — Engine will shut down. Cause: Fault simulation was enabled with a PC based service tool. Fix: With a PC based service tool, verify that the related fault simulation is not enabled. If you do not have a PC based service tool, remove battery power from the control to disable fault simulation overrides..