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Cummins/Onan NTA 855-G6 / NTA 855-G5 Engine

The Cummins/Onan NTA 855-G6 / NTA 855-G5 is an engine. It powers generator sets from Cummins/Onan, including the DFCE.

Also known as: Cummins NTA 855-G6 / NTA 855-G5

Part of the Cummins/Onan NTA855 engine family — 17 variants share parts & fitment.

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

Engine specifications

Generator sets powered by this engine

Cummins/Onan DFCE

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

Common problems

LOW DC VOLTAGE 230
Cause: Indicates battery voltage is below 24 VDC. Discharged or defective battery.
Fix: Check the battery charger fuse. Recharge or replace the battery.
EEPROM ERROR 250
Cause: Indicates PCC memory error. Data corruption of critical operating parameters.
Fix: Contact an authorized service center.
Control does not power up when the Run/Off/Auto switch is set to Run or the Self Test switch is pressed.
Cause: There is no DC power to the control.
Fix: Check for battery disconnected, discharged, or improperly connected.
UNDER FREQUENCY 313
Cause: Indicates that engine speed has dropped below 90% of nominal for 10 seconds. NOTE: Five seconds before shutdown, a Load Dump signal is initiated.
Fix: Contact an authorized service center.
SHORT CIRCUIT 322
Cause: Indicates that generator output current has exceeded 175% of rated.
Fix: Contact an authorized service center.
OVERCURRENT 320
Cause: Indicates that generator output current has exceeded 110% of rated for 60 seconds.
Fix: Contact an authorized service center.
Over Current 1471
No AC output voltage.
Fix: Contact an authorized service center.
LOW OIL PRESSURE 200
Cause: Indicates engine oil pressure has dropped to an unacceptable level.
Fix: If generator is powering critical loads and cannot be shut down, wait until next shutdown period then follow 201 Low Oil Pressure procedure. If engine can be stopped, follow 201 procedure. To check oil pressure, access Oil Pressure menu prior to clearing the fault.
LOW AC VOLTAGE 303
Cause: Indicates that one or more of the phase voltages has dropped below 85% of nominal for 10 seconds.
Fix: Contact an authorized service center.
HIGH COOLANT TEMP 211
Cause: Indicates engine has begun to overheat and coolant temperature has risen to an unacceptable level: (215° F − standby / 207° F − primary).
Fix: If generator is powering non-critical and critical loads and cannot be shut down, use the following: 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 the next procedure. To check coolant temperature, access Coolant Temp menu prior to clearing the fault.
HIGH AC VOLTAGE 301
Cause: Indicates that one or more of the phase voltages has exceeded 130% of nominal, or has exceeded 110% of nominal for 10 seconds.
Fix: Contact an authorized service center.
Engine starts from generator control panel but will not start automatically or from a remote panel. (Note: The Run/Off/Auto switch must be in the Auto position for automatic or remote starting).
Cause: Check the control wiring between the remote switch and the PCC.
Fix: Contact an authorized service center.
Weak Battery — Warning 1442
Cause: 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.
Fix: See code 441 for corrective action.
WEAK BATTERY 232
Cause: Indicates battery voltage drops below 60% of nominal for two seconds, during starting. Discharged or defective battery.
Fix: See Warning message 230, LOW DC VOLTAGE.

Compiled from service & troubleshooting documentation across every generator set that uses the Cummins/Onan NTA 855-G6 / NTA 855-G5.

Service intervals

Item	Action	Hours	Months	Notes
Genset	Inspect	8 hr		Inspect for oil, fuel, cooling and exhaust system leaks. Check exhaust system audibly and visually with set running (footnote X1).
Air Cleaner	Check	50 hr		Clean if required. Perform more often in dusty conditions (footnote X2).
Battery Charging System	Check	50 hr
Charge Air Piping	Check	50 hr
Coolant Heater	Check	50 hr		Column alignment in source table is ambiguous; interval as printed in schedule columns.
Coolant Level	Check	50 hr
Fuel Level	Check	50 hr
Oil Level	Check	50 hr
Anti-freeze and DCA Concentration	Check	100 hr		Refer to engine operation and maintenance manual for procedure (footnote X5).
Drive Belt Tension	Check	100 hr		Visually check belt for evidence of wear or slippage; replace if hard or brittle (footnote X3). Refer to engine operation and maintenance manual (footnote X5).
Exhaust Condensate Trap	Drain	100 hr
Fuel Filter(s)	Drain	100 hr		Drain 1 cup or more of fuel to remove water and sediment (footnote X4); refer to engine operation and maintenance manual (footnote X5).
Water and Sediment from Fuel Tank	Drain	100 hr		Drain 1 cup or more of fuel to remove water and sediment (footnote X4).
Air Cleaner Element	Change	250 hr		Perform more often in dusty conditions (footnote X2).
Coolant Filter	Change	250 hr		Refer to engine operation and maintenance manual for procedure (footnote X5).
Crankcase Breather	Clean	250 hr		Refer to engine operation and maintenance manual for procedure (footnote X5).
Crankcase oil and filter	Change	250 hr	12 mo	Table 7-1. If genset used for prime power, change every 6 months or 250 hours. If standby, change every 12 months or 250 hours, whichever comes first.
Starting Batteries	Check	250 hr
Cooling System	Clean	500 hr		Refer to engine operation and maintenance manual for procedure (footnote X5).
Fuel Filters	Change	500 hr		Refer to engine operation and maintenance manual for procedure (footnote X5).
Radiator Hoses for Wear & Cracks	Check	500 hr	12 mo
Rupture basin leak detect switch	Test		12 mo	Some areas may require weekly inspections by safety code.

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	Angular alignment T.I.R. limit	not more than .001	in per inch of radius	center of shaft to indicator axis
Clearance	Angular alignment maximum T.I.R.	0.001	inch per inch of radius (center of shaft to indicator axis)	measuring deflection to bolt heads
Clearance	Float switch assembly float lift clearance below C-clip stop	1/8	inch (3 mm)	use a feeler gauge
Clearance	Generator-to-engine angular alignment (T.I.R.)	.001 in. per inch of radius (center of shaft to indicator axis), maximum	in	750 kW gensets and larger
Clearance	MPU sensor to gear tooth adjustment	back out one quarter turn	turn	after contacting gear tooth
Clearance	Vibration isolator base elevation difference	0.25	inch (6 mm)	all isolator bases within this elevation of each other
Clearance	Vibration isolator clearance between top plate and base	0.25	inch (6 mm)	nominal or greater
Clearance	Vibration isolator top plate to base clearance	0.25	inch (6 mm)	nominal, or greater
Gap	Air cleaner cleaning nozzle distance	1	inch (25 mm)	at least
Gap	Angular alignment total indicator reading (T.I.R.)	0.001	inch per inch of radius	maximum
Gap	Float switch lift to test open	1/8	inch	below C-clip stop
Gap	MPU sensor to flywheel ring gear tooth	back it out one quarter turn	turn	sensor threaded in until it just touches gear tooth
Other	Air cleaner cleaning compressed air	30	psi (207 kPa)	blow from clean side, nozzle at least 1 inch (25 mm) away
Other	Angular alignment maximum T.I.R.	.001	inch per inch of radius	center of shaft to indicator axis
Other	Angular alignment maximum T.I.R.	.001 inches per inch of radius	in/in	center of shaft to indicator axis
Other	Battery electrolyte specific gravity, charge if below	1.215
Other	Battery electrolyte specific gravity, fully charged (corrected)	1.260		corrected; add 0.004 per 10°F above 80°F (27°C)
Other	Battery specific gravity, fully charged	approximately 1.260	specific gravity	at 80 F (27 C)
Other	Cool-down at idle timer range	0 to 30	minutes
Other	Fuel lift height limit	6	feet	(1.8 meters) between fuel lift pump and bottom of dip tube
Other	GOV GAIN default value for paralleling applications	70	%
Other	Maximum cranking voltage drop	2	volts	difference between battery and starter terminals while cranking
Other	Overcurrent shutdown threshold	110% of rated	% of rated	PCC time/current calculation
Other	Overcurrent warning threshold	110% of rated for 60 seconds	% of rated	generator output current
Other	Overload warning threshold	105% of standby or 115% of prime	% of rating	three-phase power output; load dump after five seconds, warning after 60 seconds
Other	REG VHZ (underfrequency roll-off) adjustable range	1 through 50; normal range 7 through 21
Other	Rated To Idle delay range	0 to 10	seconds	default = 0; Beginning Version 2.303
Other	Short circuit shutdown threshold	175% of rated	% of rated	generator output current
Other	Start Delay setting range	0 to 300	seconds	default = 0
Other	Start delay adjustment range	0 to 300	seconds
Other	Stop Delay setting range	0 to 600	seconds	default = 0
Other	Stop delay adjustment range	0 to 600	seconds
Other	Under-frequency roll-off threshold (UFRO)	typically 59 Hz for 60 Hz applications and 49 Hz for 50 Hz applications	Hz	AVR UFRO pot preset
Other	Warm-up at idle time delay range	0-300	seconds
Other	Weak battery warning threshold	below 60% of nominal for two seconds	% of nominal	during starting
Pressure	Engine oil pressure - K19 normal	50-70	psi (345-482 kPa)	run mode
Pressure	Engine oil pressure - K38 normal	45-65	psi (310-448 kPa)	run mode
Pressure	Engine oil pressure - K50 normal	50-70	psi (345-482 kPa)	run mode
Pressure	Engine oil pressure - L10/M11 normal	30-50	psi (207-345 kPa)	run mode
Pressure	Engine oil pressure - NTA 855 normal	35-50	psi (241-345 kPa)	run mode
Pressure	Engine oil pressure - V28 normal	50-90	psi (345-620 kPa)	run mode
Pressure	Engine oil pressure shutdown limit - L10/M11	20	psi (138 kPa)	run mode value
Pressure	Engine oil pressure shutdown limit - L10/M11	8	psi (55 kPa)	idle mode value
Pressure	Engine oil pressure warning limit - L10/M11	12	psi (83 kPa)	idle mode value
Pressure	Engine oil pressure warning limit - L10/M11	25	psi (172 kPa)	run mode value
Pressure	Idle oil pressure shutdown limit	12	psi (83 kPa)
Pressure	Idle oil pressure shutdown limit (PCC)	12	psi (83 kPa)	idle
Pressure	Idle oil pressure warning limit	15	psi (104 kPa)
Pressure	Idle oil pressure warning limit (PCC)	15	psi (104 kPa)	idle
Pressure	K19 engine idle oil pressure	20	psi (138 kPa)	idle
Pressure	K19 engine normal oil pressure	50-70	psi (345-482 kPa)	normal run
Pressure	K19 normal oil pressure (run/idle)	50-70 / 20	psi (345-482 / 138 kPa)	NORM run / IDLE
Pressure	K19 oil pressure shutdown limit	10	psi (69 kPa)	idle mode
Pressure	K19 oil pressure shutdown limit	35	psi (241 kPa)	run mode
Pressure	K19 oil pressure shutdown/warning limits	shutdown 35 psi (241 kPa) run; warning 40 psi (276 kPa) run; shutdown 10 psi (69 kPa) idle; warning 15 psi (103 kPa) idle	psi (kPa)
Pressure	K19 oil pressure warning limit	15	psi (103 kPa)	idle mode
Pressure	K19 oil pressure warning limit	40	psi (276 kPa)	run mode
Pressure	K38 engine idle oil pressure	20	psi (138 kPa)	idle
Pressure	K38 engine normal oil pressure	45-65	psi (310-448 kPa)	normal run
Pressure	K38 normal oil pressure (run/idle)	45-65 / 20	psi (310-448 / 138 kPa)	NORM run / IDLE

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	soft water / E.G. / DCA mixture				Cooling system to be filled with soft water/E.G./DCA mixture (on-site review checklist).
Coolant		NFPA 110	above 4°C		NFPA 110 recommends engine jacket water coolant heaters where minimum ambient is above 40°F (4°C); coolant maintained at minimum 90°F (32°C). Cooling system capacity with standard radiator: DFAB/DFAC 13 Gal (49 L); DFBF 13.5 Gal (51 L); DFCC 13.5 Gal (51 L); DFCE 15 Gal (57 L).
Engine oil		Refer to Cummins engine Operation and Maintenance Manual			Gensets are shipped with oil added. Check oil level before initial start. Keep oil level near high mark on dipstick without overfilling.
Fuel		Diesel fuel			Do not use zinc coated or copper fuel lines with diesel fuel. Fuel connection at the engine should be made with an approved flexible line.
Fuel	ASTM No. 2 diesel	Cummins engine Operation and Maintenance Manual alternate diesel fuels			Cummins engines normally use ASTM No. 2 diesel fuel. Never use galvanized or copper fuel lines, fittings or fuel tanks.
Fuel	ASTM No. 2 diesel fuel	ASTM No. 2			Cummins engines normally use ASTM No. 2 diesel fuel; they will operate on alternate diesel fuels within the specifications shown in the Cummins engine Operation and Maintenance Manual. Never use galvanized or copper fuel lines, fittings or fuel tanks.
Fuel	Diesel				Day tank fuel transfer pump maintains reservoir of diesel fuel in the day tank.
Fuel	No. 2 Diesel Fuel; Bio-Diesel B5-B20 approved with recommendations	ASTM D975 (post-storage purge fuel)			Bio-diesel not recommended for Emergency Standby RV use (low annual hours, critical start nature).
Fuel	No. 2 diesel fuel				Direct injection, number 2 diesel fuel; fuel filter; automatic electric fuel shutoff
Grease	Lithium based grease	Mobilux No. 2 or Shell Alvania R3		2.74 oz (81 ml)	Generator end bearing. Temperature range -22F to +248F (-30C to +120C). Grease should be equally divided between the bearing, bearing cap cavity, and bearing cartridge cavity.
Grease	Lithium based		-30°C to 120°C	81.0 ml	Mobilux No. 2 or Shell Alvania R3; generator end bearing; temperature range -22 F to +248 F (-30 C to +120 C); grease divided between bearing, bearing cap cavity and cartridge cavity.
Grease	Lithium based grease, Mobilux No. 2 or Shell Alvania R3		-30°C to 120°C	2.74 oz (81 ml)	End bearing lubricant; grease equally divided between bearing, bearing cap cavity and bearing cartridge cavity.

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
101	IDLE MODE	Indicates that the engine is operating in idle mode (governed at 800 RPM, generator build-up inhibited).	Warning	Remove ground from engine idle input to return to normal speed and voltage.
102	EMERGENCY STOP	Indicates local or remote Emergency Stop.	Shutdown	Turn the switch clockwise and allow it to pop out (local only). Move the Run/Off/Auto switch to Off. Press the Reset switch. Select Run or Auto, as required.
121	SPEED SIGNAL LOST	Mag pickup speed indication is not being sensed.	Shutdown	Restart and check RPM on the digital display.
135	OIL PRESSURE SENSOR H	Engine oil pressure sender signal is shorted high.	Warning	Check sender/connectors/wires.
141	OIL PRESSURE SENSOR L	Engine oil pressure sender signal is shorted low.	Warning	Check sender/connectors/wires.
143	Pre-Low Oil Pres	Indicates engine oil pressure has dropped to an unacceptable level. If generator is powering critical loads and cannot be shut down, wait until next shutdown period and then follow code 415 procedure.	Warning	If powering critical loads and cannot be shut down, wait until next shutdown period and follow code 415 procedure.
144	COOL SENSOR HIGH	Engine coolant temperature signal is shorted high.	Warning	Check sender/connectors/wires.
145	COOL SENSOR LOW	Engine coolant temperature signal is shorted low.	Warning	Check sender/connectors/wires.
146	Pre-High Coolant Temp	Indicates engine has begun to overheat (coolant temperature has risen to an unacceptable level).	Warning	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 code 151 procedure.
151	High Coolant Temp	Indicates engine has overheated (coolant temperature has risen above the shutdown trip point). Allow engine to cool down completely before proceeding.	Shutdown	Check coolant level and replenish if low; look for coolant leakage points and repair. Check for obstructions to cooling airflow. Check fan belt and repair or tighten if necessary. Check blower fan and circulation pumps on remote radiator installations. Reset control and restart after correcting problem.
197	Low Coolant Level	Indicates engine coolant level has fallen below the warning trip point (optional).	Warning	If 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.
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 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 PRES 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	Set is not operating. Warning occurs when engine coolant temperature is 70° F (21° C) or lower.	Warning	Indicates engine coolant heater is not operating or is not circulating coolant. Check coolant heater power supply, low coolant level, and heater element current draw.
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) − primary.	Warning	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 212-SHUTDOWN procedure.
212	HIGH COOLANT TEMP	Indicates engine has overheated (coolant temperature above 215° F (102° C) − standby or 207° F (97° C) − primary).	Shutdown	Allow engine to cool down completely. Check for obstructions to cooling airflow; check fan belt; check coolant mixture; check blower fan and circulation pumps on remote radiator installations. Reset control and restart.
213	COOLANT SENDER	Indicates that the resistance of the coolant temperature sender is out of range.	Warning	Check the resistance of the sender. Resistance should be 500 to 2k ohms.
214	LOW COOLANT LVL	Indicates engine coolant level has fallen below the trip point.	Warning	Allow engine to cool down completely. Check coolant level in both radiator and coolant recovery bottle and replenish if low. Look for coolant leakage points and repair if necessary.
215	LOW COOLANT LVL	Indicates engine coolant level has fallen below the trip point.	Shutdown	Allow engine to cool down completely. Check coolant level in both radiator and coolant recovery bottle and replenish if low. Reset control and restart after correcting problem. Shutdown will not occur if genset is in Idle mode (low coolant warning only).
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.
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; clean battery cable terminals and tighten. 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 after correcting the problem.
223	OVERSPEED	Engine has exceeded normal operating speed (115% ±1% of nominal).	Shutdown	Check mechanical fuel linkage and actuator; check governor output module (A38) and digital board (A32).
224	FAIL TO SYNCHRONIZE	Generator set has not synchronized to the system bus within the allowable time frame.	Warning	Check governor system stability; adjust governing and synchronizer parameters; check fuel system.
226	FAIL TO CLOSE	Paralleling breaker has been given a signal to close, but has not closed properly.	Shutdown	Verify breaker charging mechanism; check close signal; verify auxiliary contact signals.
230	LOW DC VOLTAGE	Indicates battery voltage is below 10 VDC.	Warning	Recharge or replace the battery; check the battery charger fuse. Clean and tighten battery cable connections. Check engine DC alternator; replace if normal charging voltage is not obtained. Check float level if applicable.
231	HIGH DC VOLTAGE	Indicates battery voltage exceeds 32 VDC.	Warning	Check float level on battery charger if applicable (lower float level). Check engine DC alternator; 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	Check for large block load removal, flammable vapors or leaking turbocharger seals.
235	Low Coolant Level	Indicates engine coolant level has fallen below the shutdown trip point (optional). Allow engine to cool down completely before proceeding.	Shutdown	Check coolant level and replenish if low; look for possible coolant leakage points and repair if necessary. Reset control and restart after locating and correcting problem.
240	LOW FUEL−DAY	Indicates day tank fuel supply is running low.	Warning	Check fuel supply and replenish as required.
241	LOW FUEL	Indicates day tank fuel supply is running low.	Warning	Check fuel supply and replenish as required.
250	EEPROM ERROR	PCC memory error; data corruption of critical operating parameters.	Shutdown	Perform initial start setup procedure; replace digital board (A32) if fault repeats.
251	EEPROM ERROR	PCC memory error; data corruption of noncritical operating parameters.	Warning	Perform adjustment and calibration procedures; replace digital board (A32) if fault repeats.
252	EEPROM ERROR	PCC memory error; data corruption of noncritical operating parameters.	Warning	Verify selected values; repeat save operation; replace digital board (A32) if fault repeats.
260	CUSTOMER FAULT 1	When a customer defined input is closed to ground, the corresponding fault message is displayed. Default message; editable for customer site requirements.	Warning	Fault functions can be programmed to initiate a shutdown or a warning.
261	GROUND FAULT	When a customer defined input is closed to ground, the corresponding fault message is displayed. Default message; editable for customer site requirements.	Warning	Fault functions can be programmed to initiate a shutdown or a warning.
262	RUPTURE BASIN	When a customer defined input is closed to ground, the corresponding fault message is displayed. Default message; editable for customer site requirements.	Warning	Fault functions can be programmed to initiate a shutdown or a warning.
263	HIGH GEN TEMP	When a customer defined input is closed to ground, the corresponding fault message is displayed. Default message; editable for customer site requirements.	Warning	Fault functions can be programmed to initiate a shutdown or a warning.
270	PHASE ROTATION	The phase relationship between the generator set and the system bus is not matched.	Shutdown	Verify genset phase rotation matches bus; verify control wiring to bus PT module.
272	FIRST START	PowerCommand control is not receiving a proper signal from the system master first start sensor.	Warning	Verify Master First Start Sensor and interconnection wiring.
301	HIGH AC VOLTAGE	One or more phase voltages exceeded 130% of nominal, or exceeded 110% of nominal for 10 seconds.	Shutdown	Check PCC, alternator, excitation circuit, and PT/CT module wiring.
303	LOW AC VOLTAGE	One or more phase voltages dropped below 85% of nominal for 10 seconds.	Shutdown	Check PMG/field wiring, rotating rectifier, load and connectors.
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 fuel supply, intake air supply and load.
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.
337	LOSS OF EXCITATION	Alternator excitation system is improperly adjusted or has failed.	Shutdown	Check output voltage calibration, load sharing lines, and leading power factor loads.
359	Fail To Start	Indicates possible fuel system problem (engine cranks but fails to start).	Shutdown	Check for empty fuel tank, fuel leaks, or plugged fuel lines and correct as required. 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 after correcting the problem.
415	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.
421	Oil Temp	Indicates engine has begun to overheat (oil temperature has risen to an unacceptable level) (optional).	Warning	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 code 151 procedure and also check engine oil level.
441	Low Bat Voltage	Indicates battery voltage supply to the control is approaching a low level at which unpredictable operation will occur.	Warning	Check for discharged or defective battery; check the battery charger fuse; recharge or replace the battery. Clean battery cable terminals and tighten all connections. Check battery charge voltage float level if applicable (raise float level).
442	High Bat Voltage	Indicates battery voltage supply to the control is approaching a high level at which damage to the control can occur.	Warning	Check float level on battery charger if applicable (lower float level).
1122	Rated/Idle Trans
1123	SHUTDOWN AFTER BS	Shutdown fault occurred while Battle Short was enabled and then disabled.	Shutdown	Review Fault History and perform corrective action.
1124	DELAYED SHUTDOWN	Shutdown fault became active while Delayed Shutdown feature was enabled.	Warning	Review Fault History and perform corrective action.
1131	BATTLE SHORT ACTIVE	Control is in Battle Short mode.	Warning	Bypasses several critical fault shutdowns for emergency operation.
1311	Customer Input #1	The nature of the fault is an optional customer selection. Example inputs: Low Fuel Day Tank, Water In Fuel, Ground Fault, Low Starting Hydraulic Pressure, Low Starting Air Pressure, etc.		Enable/disable input (Default: enable); Status, Warning or Shutdown (Default: #1-None, #2 thru #4-Warning); Active closed or open (Default: closed [ground]); change display name up to 19 characters (Default: #1-Customer Fault 1).
1311, 1312, 1317, 1318	CUSTOMER INPUT #1 - #4	Optional customer-selected fault input is active.	Warning	Check external wiring and active input (closed/open) selection.
1312	Customer Input #2	Default display name: Ground Fault.		Configurable input; defaults #2 thru #4 = Warning.
1317	Customer Input #3	Default display name: Low Fuel.		Configurable input; defaults #2 thru #4 = Warning.
1318	Customer Input #4	Default display name: Rupture Basin Fault.		Configurable input; defaults #2 thru #4 = Warning.
1334	CRIT SCALER OR	Incorrect feature or calibration entered into control.	Shutdown	Reload correct calibration.
1335	NONCRIT SCALER OR	Incorrect feature or calibration entered into control.	Warning	Reload correct calibration.
1337	No Message
1416	FAIL TO SHUTDOWN	Genset continues to run after shutdown command.	Warning	Check Battle Short feature enabled condition.
1417	Powr Down Error	Indicates that the controller can not power down because of some unknown condition. Possible drain on battery.	Warning	Contact an authorized service center for service.
1433	Emergency Stop	Indicates local Emergency Stop.	Shutdown	To reset: pull the button out; move the O/Manual/Auto switch to O; press the front panel Fault Acknowledge/Reset button; select Manual or Auto as required.
1434	Remote E-Stop	Indicates remote Emergency Stop.	Shutdown	See code 1433 to reset.
1435	Engine Cold	Engine jacket water coolant temperature falls below 70°F (21°C); Warning LED illuminated (provided to meet NFPA 110 requirements)	Warning	Check the coolant heaters for proper operation
1438	Fail To Crank	Indicates possible fault with control, speed sensing or starting system.	Shutdown	See code 441 for corrective action.
1442	Weak Battery	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.	Warning	See code 441 for corrective action.
1443	Battery Failed	Dead battery - engine will not start.	Shutdown	See code 441 for corrective action.
1444	KW OVERLOAD	Generator output power exceeded 105% of genset rating.	Warning	Check load and load lead connections; check CTs.
1445	SHORT CIRCUIT	Generator output current has exceeded 175% of rated.	Shutdown	Check load and load lead connections.
1446	HIGH AC VOLTAGE	One or more phase voltages exceeded 130% of nominal.	Shutdown	Check fault simulation, load removal, threshold settings, Base board/generator.
1447	LOW AC VOLTAGE	Phase voltages dropped below 85% of nominal for 10 seconds.	Shutdown	Check overload, output terminal connections, PMG/field wiring, rectifier diodes.

Showing the first 80 of 123 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

Adjust Start/Stop Delays (PCC Adjust Menu) adjustment

⚠ Electrostatic discharge will damage circuit boards. Always wear a grounding wrist strap when working inside control box.

Press the button next to ADJUST in the Main Menu; the VOLTAGE submenu appears.
Press the button next to >> to move through VOLTAGE and FREQUENCY to the START DELAY submenu.
Use the buttons next to the up and down symbols to set the start delay.
Press >> to move to the STOP DELAY submenu and set the stop delay.
Press >> to move to the IDLE SPEED submenu and set idle speed (only in idle mode).
Press >> to move to SAVE/EXIT; select SAVE then EXIT to return to Main menu.

Adjusting Values/Parameters (PCC Adjust Menu) adjustment

Press the button next to the arrow symbol in the display until the + and - symbols are displayed.
If necessary, press the button next to the arrows to move to the numeric character to change.
Press + to increase the value or select the parameter; press - to decrease the value or select the parameter.
Press the save symbol to save changes; changes are not saved if Home or Previous Main Menu is pressed first.

Aligning Generator with Engine (Angular Alignment) adjustment

⚠ Accidental starting of the generator set during this procedure presents the hazard of severe personal injury or death.

Tools: Dial indicator, Shims

Disconnect the negative (-) battery cable(s) before beginning.
Fasten a dial indicator to the generator shaft or cooling fan with the sensing point on the capscrew head or flat surface of the drive disc at the bolt circle diameter.
Bar the engine over in a clockwise rotation as viewed from engine flywheel; do not allow it to roll back on compression.
Determine the total indicator reading (T.I.R.) as the sum of the maximum positive and negative dial indicator readings over one revolution.
Measure the distance from the center of the generator shaft to the indicator measuring point.
Measure the distance from the generator side of the flex discs to the center of the generator mounting bolt.
Compare the distances; multiply this ratio times one half the T.I.R. to approximate the amount of shims to remove or add.

Angular Alignment Procedure adjustment

⚠ Accidental starting of the generator set during this procedure presents the hazard of severe personal injury or death. Make sure to disconnect the negative (-) battery cable(s) before beginning.

Tools: Dial indicator, Wooden shims

Disconnect the negative (-) battery cable(s) before beginning.
Fasten a dial indicator to the generator shaft or cooling fan with sensing point on capscrew head or flat surface of drive disc at bolt circle diameter.
Bar the engine over in a clockwise rotation as viewed from engine flywheel; do not allow it to roll back on compression.
Record maximum positive and negative dial indicator readings as the engine completes one revolution.
T.I.R. equals the sum of the maximum positive and negative readings.
Maximum T.I.R. should not be more than .001 inch for each inch of radius.
Remove equal shims from under both generator mounting feet to lower the generator.

Angular Alignment Procedure (750 kW Gensets and Larger) adjustment

⚠ Accidental starting of the generator set during this procedure presents the hazard of severe personal injury or death. Make sure to disconnect the negative (-) battery cable(s) before beginning.

⚠ Do not bar engine over by prying on fan blade.

Tools: Dial indicator, Shims

Disconnect the negative (-) battery cable(s) before beginning.
Fasten a dial indicator to the generator shaft or cooling fan, with the sensing point on the capscrew head or drive disc flat surface at bolt circle diameter.
Bar the engine over clockwise as viewed from the engine flywheel; do not allow it to roll back on compression.
Total indicator reading (T.I.R.) is the sum of the maximum positive and negative readings as the engine completes one revolution.
To lower the generator, remove equal shims from under both generator mounting feet; approximate shim amount from the distance ratio.

Angular Alignment Procedure (Generator to Engine) adjustment

⚠ Accidental starting during this procedure presents the hazard of severe personal injury or death.

⚠ Do not bar engine over by prying on fan blade.

Tools: dial indicator

Disconnect the negative (-) battery cable(s) before beginning.
Fasten a dial indicator to the generator shaft or cooling fan with sensing point resting on the drive disc capscrew head/flat surface at the bolt circle diameter.
Bar the engine over in a clockwise rotation as viewed from the engine flywheel; do not allow it to roll back on compression at the end of travel of each reading.
Record the total indicator reading (T.I.R.) as the sum of the maximum positive and negative dial indicator readings over one engine revolution.
Compare the measured T.I.R. to the maximum allowed (.001 in. per inch of radius from center of shaft to indicator axis); add or remove shims under the generator mounting feet to correct.

Axial Alignment Procedure adjustment

Tools: Dial indicator, Magnetic base or clamp

Check axial alignment only when an objectionable vibration is present after angular alignment.
Fasten dial indicator holding device to skid base, engine block, or generator shell with a magnetic base or clamp; rest sensor on generator shaft hub.
Bar the engine over clockwise through a couple of rotations; record indicator readings at eight equally spaced points around the shaft diameter.
To correct out-of-tolerance T.I.R., remove the drive disc capscrews, mark discs and flywheel, rotate 180 degrees from original location, retorque, and recheck.
If unchanged, rotate the discs to 30, 60 or 90 degrees from their original location.

Axial Alignment Procedure (Generator to Engine) adjustment

Tools: dial indicator

Fasten a dial indicator holding device to the skid base, engine block, or generator shell with the sensor point resting on the generator shaft hub.
Bar the engine over in a clockwise rotation through a couple of rotations, recording indicator readings at eight equally spaced points around the shaft diameter to obtain axial T.I.R.
Reduce the measured T.I.R. runout by one half if excessive vibration remains after angular alignment.

Governor Calibration Checks adjustment

Tools: Frequency meter or tachometer, Jumper wire

Start the generator set.
Adjust engine no-load speed to the desired allowable speed droop using the Run Speed potentiometer.
With no load, turn GAIN clockwise slowly until engine speed oscillates.
Reduce GAIN slowly counterclockwise until engine speed is stable.
Upset the governor by momentarily shorting terminals 7 and 10 on the governor control.
Apply and remove loads to check generator set response.

HC4-7 Axial Alignment Procedure adjustment

Tools: Dial indicator with magnetic base or clamp

Check only when an objectionable vibration is present.
Fasten dial indicator holding device to skid base, engine block, or generator shell with magnetic base or clamp.
Position sensor point on the generator shaft hub.
Bar the engine over in a clockwise rotation as viewed from engine flywheel through a couple of rotations.
Record indicator readings in eight equally spaced points around the shaft diameter.
Remove the capscrews connecting drive discs and flywheel and mark discs and flywheel.
Rotate engine or generator so drive disc holes are repositioned 180 degrees from original location.
Put capscrews back in and retorque. Recheck shaft alignment.
If runout unchanged, rotate discs to 30, 60 or 90 degrees from original location.
If T.I.R. does not improve, inspect flywheel pilot and drive disc runouts.

P7 Axial Alignment Procedure adjustment

Check only when an objectionable vibration is present.
Remove the capscrews connecting drive discs and flywheel.
Mark the drive discs and flywheel with respect to each other.
Rotate engine or generator so drive discs holes are repositioned two bolt holes from original location.
Put capscrews back in and retorque. Recheck/record vibration levels.
Repeat this test until drive disc holes are repositioned 180 degrees from original location.
Review vibration data and position drive disc in lowest recorded level location.

UFRO Adjustments adjustment

⚠ Use an insulated handle screw driver to prevent electrical shock.

Tools: Insulated handle screwdriver, Frequency meter or tachometer

Make a note of the no-load frequency.
Determine roll-off frequency by turning the governor speed pot until the LED lights; if okay go to step 5.
Adjust the governor speed pot to the proper roll-off frequency.
Turn the UFRO pot until LED goes off, then slowly turn it back until the LED just goes on.
Adjust the governor speed pot back to the initial frequency setting.

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
		12 lead generator sets	Load wires are routed through the CTs	Reconnectable gensets (12 leads) have dual secondary CTs (3 pins); CT wire 2/3 to pin 2 (high voltage) or pin 3 (low voltage).
		6 lead generator sets	Generator output leads are routed through the CTs	Non-reconnectable gensets (6 leads) have single secondary CTs (2 pins).
		Cummins PowerCommand generic AC Reconnect Wiring Diagram 625-2755 (Rev. D) and 625-3100 (Rev. F)		Applies to models DFAA, DFAB, DFAC, DFBF, DFCB, DFCC, DFEB, DFEC, DFFB, DFGA, DFGB, DFJA, DFJB, DFJC, DFJD, DFLB, DFLC, DFLD, DFMB (625-2755) and models DFAA-DFMB plus DFCE, DFED, DQAA, DQAB, DQBA, DQBB (625-3100).
		Current transformers CT21-U load leads (A phase), CT22-V load leads (B phase), CT23-W load leads (C phase)	CT secondary wire marked 1 to pin 1; wire marked 2/3 to pin 2 for high voltage gensets or pin 3 for low voltage gensets	CT dot must face toward the generator; CTs have dual secondaries (3 pins).
		Generator load terminals stamped U, V, W and N (U=L1, V=L2, W=L3, N=L0)	Stranded load wires bolted to generator reconnection terminal block or circuit breaker lugs	Available generator output voltages and maximum current ratings are specified on the generator set nameplate; line-to-neutral is the lower voltage, line-to-line the higher. Reconnection diagram is located on the upper side cover of the control housing.
	A	CT21 – U load leads	A phase	CT dot must face the generator; CT terminal 1 connects to metering circuit; terminal 2/3 connects to ground.
	A (U)	Bus PT module TB1 A	bus A phase	Bus PT module A39.
	A (U)	CT21	U load leads (A phase)	CT dot must face the generator; CT terminal 1 connects to metering circuit, terminal 2/3 to ground.
	B	CT22 – V load leads	B phase	CT dot must face the generator; CT terminal 1 connects to metering circuit; terminal 2/3 connects to ground.
	B (V)	Bus PT module TB1 B	bus B phase	Bus PT module A39.
	B (V)	CT22	V load leads (B phase)	CT dot must face the generator; terminal 1 to metering circuit, terminal 2/3 to ground.
	C	CT23 – W load leads	C phase	CT dot must face the generator; CT terminal 1 connects to metering circuit; terminal 2/3 connects to ground.
	C (W)	Bus PT module TB1 C	bus C phase	Bus PT module A39.
	C (W)	CT23	W load leads (C phase)	CT dot must face the generator; terminal 1 to metering circuit, terminal 2/3 to ground.
	N	Bus PT module TB1 N	bus neutral	Bus PT module A39.
110 V - 120 V L-N	1	Single phase, 2-wire		PTC module jumper locations
115/200	Three Phase	Reconnectable
120/208	Three Phase	Reconnectable
120/240	Three Phase	Reconnectable
139/240	Three Phase	Reconnectable
190 V - 240 V L-L	3	Three phase		Use PTC module 0300-5382-01; 50/60 Hz
200 V - 240 V L-L	1	Single phase, 3-wire		PTC module jumper locations
277/480	Three Phase	Non-Reconnectable
277/480	Three Phase	Reconnectable
347/600	Three Phase	Non-Reconnectable
380 V - 600 V L-L	3	Three phase		Use PTC module 0300-5382-02; 50/60 Hz
high voltage genset		12-lead CT secondary wire marked 2/3 to pin 2	2/3	For high voltage gensets.
low voltage genset		12-lead CT secondary wire marked 2/3 to pin 3	2/3	For low voltage gensets.

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 NTA855 family

Part #	Description	Category
140-1346	Air Cleaner (Includes Element)	Air filter
140-2391	Element - Air Cleaner (Standard)	Air filter
140-2392	Element, Air Cleaner - Primary	Air filter
140-2393	Element, Air Cleaner - Safety	Air filter
511-0084	Belt, Charging Alternator	Belt
511-0160	Belt, Drive - V (Fan)	Belt
319-2236	Bracket, Mounting	Bracket
518-0548-58	Clamp, Hose	Clamp
130-3537	CE 1 130-3541 3318318 CE 1 4 501-0551 1 5 503-1467-07 1 503-0189 2 505-0022 1 502-0827	Coolant filter
130-3541	Filter, Water - w/Corrosion Inhibiting Chemical DCA4 (Pre-Charging)	Coolant filter
0300-4623-09	DFCB (600V)	Current transformer
0300-4623-10	DFCC (600V)	Current transformer
0300-4623-24	DFCB BR (0-480V)	Current transformer
0300-4623-27	DFCC BR (0-480V)	Current transformer
155-2287-02	Gasket, Flange (used with 155-2281 Elbow)	Gasket
501-0551	Line, Fuel - Flexible (Bypass line)	Hose
503-1467-07	Hose, Rubber (3/4" ID x 33" LG) Radiator to Filter Housing	Hose
503-1679-02	Hose, Rubber - Upper	Hose
505-1414-01	Hose, Rubber - Lower	Hose
122-0526	Element, Filter	Oil filter
122-0755	Lube & Bypass Filter (Latest Style Used In Engine Manufacturing)	Oil filter
LF3000	Lube, Spin-On	Oil filter
100-1359	Engine, Replacement (Cummins NTA855G)	Service part / kit
102-1335	Plug, Oil Drain	Service part / kit
305-0813-02	CUMMINS battery charger 208VAC/24VDC/10A	Service part / kit
307-2621-02	Relay, Start Solenoid (K4)	Service part / kit
309-0437	(222"F)	Service part / kit
504-0011	Valve, Shutoff (1/2”)	Service part / kit
505-0019	Bushing, Pipe - Reducer 1/2” to 3/8”, DFBF (1/2” to 3/8”) 505-0131 DFCB, DFCC, DFCE (3/4” to 3/8”)	Service part / kit
505-0100	Nipple, Pipe - Close (1/2”)	Service part / kit
526-0029	*Washer, Flat (1/2")	Service part / kit
526-0219	Washer, Flat (1/2)	Service part / kit
800-0048	Screw, Cap - Hex Head (3/8-16 x 3/4”)	Service part / kit
800-0092	Screw, Cap - Hex Head (1/2-13 x 1.5)	Service part / kit
850-0050	Washer, Lock - Spring (3/8”)	Service part / kit
870-0212	Nut, Locking (1/4-20)	Service part / kit
903-0124	NA	Service part / kit
903-0204	NA	Service part / kit
903-0500	NA	Service part / kit
903-0604	NA	Service part / kit
E204747	Coolant heater 240/480V 6420W 1PH	Service part / kit
508-0292	Washer, Sealing - Copper	Seal
151-0411	Pickup, Magnetic	Sensor
193-0244	Sender, Oil Pressure (E1)	Sensor
193-0375	Sender, Coolant	Sensor
193-0432	Sender, Oil Temperature (S2 Engine Block, E4 Oil Pan)	Sensor
309-0179	Switch, High Water Temperature (Standard Part) Side Mounted On Water Outlet Housing	Sensor
309-0269	Sender, Temperature-Lo Engine	Sensor
333-0407	Switch, Pressure - Oil, 14# PSI (SHUTDOWN) With Dual Terminals	Sensor
960-0504	PCC Control Service Manual	Service manual
960-0507	Detector Control Service Manual	Service manual

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 NTA 855-G6 / NTA 855-G5 engine?

The Cummins/Onan NTA 855-G6 / NTA 855-G5 powers 1 generator set(s), including Cummins/Onan DFCE.

What is a common problem with the Cummins/Onan NTA 855-G6 / NTA 855-G5 engine?

A commonly reported issue on generators using the Cummins/Onan NTA 855-G6 / NTA 855-G5 is: LOW DC VOLTAGE. Cause: Indicates battery voltage is below 24 VDC. Discharged or defective battery.. Fix: Check the battery charger fuse. Recharge or replace the battery..