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

Name: Cummins/Onan NTA 855-G6 / NTA 855-G5 Engine
Brand: Cummins/Onan

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 NTA 855 engine family — 5 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

UNDER FREQUENCY 313
Fix: Shutdown
SHORT CIRCUIT 322
Fix: Shutdown
Over Current 1471
LOW OIL PRESSURE 200
Fix: Shutdown
Low Coolant Level 197
LOW AC VOLTAGE 303
Fix: Shutdown
High Coolant Temp 211
Fix: Indicates engine has begun to overheat and coolant temperature has risen to an unacceptable level: (215° F − standby / 207° F − primary).
HIGH AC VOLTAGE 301
Fix: Shutdown
Weak Battery 1442
Warning, Shutdown, and Non-Automatic lamps are not lit. Digital display shows main menu or selected menu.
Cause: Indicates all engine systems are normal. No corrective action required
Warning lamp lights. MESSAGE: WEAK BATTERY 232 - WARNING 232
Fix: Indicates battery voltage drops below 60% of nominal for two seconds, during starting. a. Discharged or defective battery. See Warning message 230, LOW DC VOLTAGE.
Warning lamp lights. MESSAGE: RUPTURE BASIN 262
Warning lamp lights. MESSAGE: OVERLOAD 330
Fix: 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. Contact an authorized service center.
Warning lamp lights. MESSAGE: OVERCURRENT 320
Fix: Indicates that generator output current has exceeded 110% of rated for 60 seconds. Contact an authorized service center.
Warning lamp lights. MESSAGE: LOW FUEL DAY 240 - WARNING 240
Fix: Indicates day tank fuel supply is running low. Check fuel supply and replenish as required.

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	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
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	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	Cool-down at idle timer range	0 to 30	minutes
Other	GOV GAIN default value for paralleling applications	70	%
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	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	Warm-up at idle time delay range	0-300	seconds
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 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	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 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	K50 engine idle oil pressure	20	psi (138 kPa)	idle
Pressure	K50 engine normal oil pressure	50-70	psi (345-482 kPa)	normal run
Pressure	K50 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	L10/M11 engine idle oil pressure	15	psi (103 kPa)	idle
Pressure	L10/M11 engine normal oil pressure	30-50	psi (207-345 kPa)	normal run
Pressure	L10/M11 oil pressure shutdown limit	20	psi (138 kPa)	run mode value
Pressure	L10/M11 oil pressure shutdown limit	8	psi (55 kPa)	idle mode value
Pressure	L10/M11 oil pressure warning limit	12	psi (83 kPa)	idle mode value
Pressure	L10/M11 oil pressure warning limit	25	psi (172 kPa)	run mode value
Pressure	Low oil pressure shutdown (Detector)	14	psi (97 kPA)
Pressure	NTA 855 engine normal oil pressure	35-50	psi (241-345 kPa)	normal run
Pressure	NTA 855 oil pressure shutdown limit	25	psi (172 kPa)	run mode value
Pressure	NTA 855 oil pressure shutdown limit	8	psi (55 kPa)	idle mode value
Pressure	NTA 855 oil pressure warning limit	12	psi (83 kPa)	idle mode value
Pressure	NTA 855 oil pressure warning limit	30	psi (207 kPa)	run mode value
Pressure	Normal engine oil pressure (PCC)	35-50	psi (242-345 kPa)
Pressure	Normal oil pressure	35-50	psi (242-345 kPa)
Pressure	Oil pressure shutdown limit	25	psi (172 kPa)

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).
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. Grounding the engine idle input causes generator build-up to be inhibited and the engine to be governed at 800 RPM.	Warning	Remove ground from engine idle input to return to normal speed and voltage.
102	EMERGENCY STOP	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.
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 Sh Active	Control is in Battle Short mode.	Warning	Bypasses several critical fault shutdowns for emergency operation.
121	Speed Signal Lost	Mag pickup speed indication is not being sensed.	Shutdown	Restart and check RPM on the digital display.
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
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.
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.
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.
1433	Emergency Stop	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	Remote Emergency Stop.	Shutdown	See code 1433 to reset.
1435	Low Coolant Temp	Warning occurs when engine coolant temperature is 70°F (21°C) or lower. In applications where the ambient temperature falls below 40°F (4°C), Low Coolant Temp may be indicated even though the coolant heaters are operating.	Warning	Indicates engine coolant heater is not operating or is not circulating coolant. Check that coolant heater is connected to power supply (check for blown fuse or disconnected heater cord). Check for low coolant level and replenish if required; look for possible coolant leakage points and repair as required.
1438	Fail To Crank	Indicates possible fault with control, speed sensing or starting system.	Shutdown	See code 441 for corrective action.
144	Coolant Sensor High	Engine coolant temperature signal is shorted high.	Warning	Check sender/connectors/wires.
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.
1448	Under Frequency	Engine speed dropped below 90% of nominal for 10 seconds.	Shutdown	Check fuel supply, intake air supply and load.
1449	Over Frequency	Frequency is 10% above base frequency for 20 seconds.	Warning	Check fuel or air delivery; check connections.
145	Coolant Sensor Low	Engine coolant temperature signal is shorted low.	Warning	Check sender/connectors/wires.
1452	Gen CB Not Close	Genset circuit breaker (S2) failed to close when PTC is enabled.	Warning	Refer to Section 5 troubleshooting charts.
1453	Gen CB Not Open	Genset circuit breaker (S2) failed to open when PTC is enabled.	Warning	Refer to Section 5 troubleshooting charts.
1459	Reverse Power	Improper CT phasing.	Shutdown	Check wiring to voltage sense circuit; refer to CT Installation in Section 6.
146	Pre-High Coolant Temp	Indicates engine has begun to overheat (coolant temperature has risen to an unacceptable level).	Warning	Reduce load; check air inlets/outlets; follow code 151 if engine can be stopped.
1461	Loss Of Field	Loss of field (electric) due to reverse kVAR.	Shutdown	Check excitation circuit.
1466	Modem Failure	Control cannot communicate with the modem.	Warning	Check for open, short to ground and loose connections to the modem.
1468	Network Error	Momentary loss of communication from the LonWorks Network.	Warning	Refer to LonWorks Network publications.
1469	Speed/Hz Match	Measured speed and measured AC output frequency do not agree.	Shutdown	Check calibration file.
1471	Over Current	Generator output current exceeded 110% of rated for 60 seconds.	Warning	Check load and load lead connections.
1472	Over Current	Output current exceeded 110% of rated and time/current calculation initiated shutdown.	Shutdown	Check load and load lead connections.
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 powering critical loads, wait until next shutdown period then follow 201 procedure.
201	LOW OIL PRESSURE	Indicates engine oil pressure has dropped below the shutdown trip point.	Shutdown	Check oil level, lines and filters; replenish if low; reset control and restart; contact service center.
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. Contact service center.
210	LOW COOLANT TEMP	Warning occurs when engine coolant temperature is 70°F (21°C) or lower.	Warning	Warning LED illuminates. Check the coolant heaters for proper operation; if operating properly, other precautions may be necessary to warm the engine before applying a load.
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; check air inlets/outlets and remove obstructions.
212	Oil Temp Sensor H	Indicates engine has overheated (coolant temperature above 215° F (102° C) − standby or 207° F (97° C) − primary).	Warning	Check sender/connectors/wires.
213	Oil Temp Sensor L	Resistance of the coolant temperature sender is out of range.	Warning	Contact an authorized service center.
214	LOW COOLANT LVL	Indicates engine coolant level has fallen below the trip point.	Warning	Check coolant level in radiator and coolant recovery bottle; replenish if low; look for leaks.
215	LOW COOLANT LVL	Indicates engine coolant level has fallen below the trip point.	Shutdown	Allow engine to cool; check coolant level and replenish; look for leaks and repair; reset and restart. Shutdown will not occur in Idle mode.
220	MAG PICKUP	Mag pickup speed indication not sensed or does not match generator set output frequency.	Shutdown	Restart and check RPM; check PCC model setting; inspect and test MPU.
221	FAIL TO CRANK	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	Possible fuel system problem.	Shutdown	Check for empty fuel tank, leaks, plugged fuel lines; replace dirty fuel or air filter; reset and restart.
223	OVERSPEED	Indicates engine has exceeded normal operating speed. (115% ±1% of nominal).	Shutdown	Contact an authorized service center.
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	Lower battery charger float level if applicable; check engine DC alternator.
232	WEAK BATTERY	Indicates battery voltage drops below 60% of nominal for two seconds, during starting.	Warning	See Warning message 230, LOW DC VOLTAGE.
2327	PTC Fault	PTC module or communication link is not working properly.	Warning	Check PTC module power, ground shield, cycle control power.
2329	Low S1 Frequency	Low utility (S1) frequency.	Warning	Check S1 AC inputs and wiring to PTC at TB5; check sensor set points.
2331	Low S1 Voltage	Low utility (S1) voltage.	Warning	Check S1 AC inputs and wiring to PTC at TB5; check pickup/dropout set points.
2335	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.
2336	Memory Error	Control memory error; data corruption of critical operating parameters.	Shutdown	Try reloading calibration file.
2337	Pwr Tran Disabled	PTC module available but PTC feature not enabled.	Warning	Enable PTC feature with InPower; cycle control power.
2338	Pwr Tran Failure	Control could not communicate with the PTC module.	Warning	Check PTC module power and cable ground shield; cycle control power.
2339	Pwr Down Enabled	Power Down (sleep) enabled but PTC module or network board is active.	Warning	None required.
234	Overspeed	Engine has exceeded normal operating speed.	Shutdown	Check for large block load removal, flammable vapors or leaking turbocharger seals.
2341	High Control Temp	Control temperature above 158 F (70 C) for longer than set time.	Warning	Check genset room air flow.
2342	Too Long In Idle (10 min.)	Indicates genset has been in Idle mode too long (10 minutes maximum).	Warning	Exit idle mode.
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; reset control.
2358	High S1 Voltage	Utility (S1) voltage increased above the over-voltage threshold.	Warning	Measure S1 AC inputs at PTC module; check sensor set points.
2396	S1 CB Not Close	Utility contact (S1) failed to close with PTC enabled.	Warning	Refer to Section 5 troubleshooting charts.
2397	S1 CB Not Open	Utility contact (S1) failed to open with PTC enabled.	Warning	Refer to Section 5 troubleshooting charts.
240	LOW FUEL−DAY	Indicates day tank fuel supply is running low.	Warning	Check fuel supply and replenish as required.

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 (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.

Voltage Adjustment adjustment

⚠ Do not adjust the factory-sealed V/HZ break point pot.

⚠ Hazardous voltage inside output box.

Remove the protective cover for access to the voltage adjusting pot and 50/60 Hz selector switch.
Check the position of the 50/60 Hz selector switch and change if necessary.
Adjust no-load voltage as required.
Replace the cover.

Cooling System Test (LAT calculation) diagnostic

Tools: Load bank, Thermocouples (No. 24 AWG or lighter)

Complete a representative installation.
Load the genset to rated full-load using a load bank.
Conduct the test at ambient >= 21 C (70 F).
Measure engine coolant outlet temperature and shielded ambient air temperature with thermocouples.
Expel air from the coolant system before testing; add coolant as necessary.
Run at full-load and record temperatures at 15-minute intervals until stable.
Calculate LAT = T(max) 107C - T(test) + T(amb); goal LAT >= 40 C (104 F).

Generator/Base Board Isolation Procedure diagnostic

⚠ This test involves unregulated excitation of the generator.

⚠ Hazardous voltage; use insulated tools and stand on dry platform.

Tools: Voltmeter, Jumper leads, 12V battery

Throw line circuit breaker OFF and shut down the set.
Disconnect exciter stator leads X and XX from AC harness.
Prepare to measure output voltage across generator terminals.
Bring 12V battery jumpers to X (Field +) and XX (Field -).
Verify polarity is correct before connecting.
Start set; connect battery negative to XX lead.
If rated voltage and balanced phases, generator is OK.
If unbalanced troubleshoot main stator; if low troubleshoot exciter circuits.

Generator/PCC Control Isolation Procedure diagnostic

⚠ HIGH VOLTAGE. Touching uninsulated high voltage parts inside the control box can result in severe personal injury or death.

Tools: Voltmeter, Jumpers, 12 volt battery

Throw the line circuit breaker OFF and shut down the set.
Remove accessory box cover; remove plug P10 from A37 J10.
Prepare to measure output voltage across generator terminals.
Connect 12V battery jumpers to X (P10-6 red) and XX (P10-3 brown).
Check polarity; incorrect polarity makes the test inconclusive.
Start set and connect battery negative to the XX lead.
Rated or higher balanced voltage means generator circuitry is OK.
Unbalanced voltage: troubleshoot main stator; low voltage: exciter/field.

Ground Fault Relay Test diagnostic

Verify that the N-G Fault Indicator on the GFR is not lit; if lit, the neutral-to-ground bonding jumper circuit is open.
Move the control switch to the Run position.
Press the TEST switch on the ground fault relay.
Verify that the control panel warning message is displayed and the Fault Indicator (>I) on the GFR is lit.
Reset the control panel fault, which also resets the ground fault relay.

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 (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 (V)	CT22	V load leads (B phase)	CT dot must face the generator; terminal 1 to metering circuit, terminal 2/3 to ground.
	C (W)	CT23	W load leads (C phase)	CT dot must face the generator; terminal 1 to metering circuit, terminal 2/3 to ground.
110 V - 120 V L-N	1	Single phase, 2-wire		PTC module jumper locations
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
380 V - 600 V L-L	3	Three phase		Use PTC module 0300-5382-02; 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.

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: UNDER FREQUENCY. Fix: Shutdown.