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Cummins/Onan KTTA50-G2 Engine

The Cummins/Onan KTTA50-G2 is a 50.3 L 16-cylinder turbocharged and aftercooled engine rated at 1800 rpm, producing up to 1656.1 kW. It powers generator sets from Cummins/Onan, including the DFM. It holds 151.4 L (40.0 gal) of oil.

Also known as: Cummins KTTA50-G2

Part of the Cummins/Onan KTTA50 engine family — 3 variants share parts & fitment.

50.3 L

Displacement

Cylinders

1800 rpm

Rated speed

1656 kW

Gross power

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

Engine specifications

Oil capacity	151.4 L
Displacement	50.3 L
Cylinders	16
Aspiration	turbocharged and aftercooled
Rated speed	1800 rpm
Gross power	1656 kW

Generator sets powered by this engine

Cummins/Onan DFM

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

Common problems

LO OIL PRES lamp lights
Cause: Low coolant level
Fix: Check for low coolant level and replenish if required; look for possible coolant leakage points and repair as required
EEPROM ERROR — Warning 251
Cause: Indicates PCC memory error. Data corruption of noncritical operating parameters.
Fix: Contact an authorized service center.
WEAK BATTERY — Warning 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.
Warning, Shutdown, and Non-Automatic lamps are not lit. Digital display shows main menu or selected menu.
Cause: Indicates all engine systems are normal.
Fix: No corrective action required.
UNDER FREQUENCY — Shutdown 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.
The FAULT 1 or FAULT 2 fault lamp lights; engine shuts down immediately
Cause: The standard undesignated fault functions are programmed to shut down the set when engine runs fo
The FAULT 1 or FAULT 2 fault lamp lights. Engine shuts down immediately, or engine continues to run. FAULT 1 or FAULT 2
Fix: A. Fault lamp on. Correct fault and reset control. b. Poor battery cable connections. Clean the battery cable terminals and tighten all connections. c. Discharged or defective battery. Recharge or replace the battery.
The FAULT 1 or FAULT 2 fault lamp lights. Engine shuts down immediately, engine runs for several seconds and then shuts down, or engine continues to run.
Cause: The standard undesignated fault functions are programmed to shut down the set when a fault is sensed. Fault 1 is time delayed while Fault 2 is immediate. The nature of the fault is an optional selection that is determined when the set installation is designed. The undesignated fault functions may also be programmed for non-shutdown or non-time delay.
The BASIN (optional) fault lamp lights. Engine continues to run or is in standby mode. (Engine can be programmed to shut down.)
Cause: Indicates fuel is leaking from inner tank to outer basin or the sensor may be defective.
Fix: Contact an authorized service center for service.
SWITCH OFF lamp flashes.
Cause: Indicates Run/Stop/Remote switch is in the Stop position which will prevent automatic starting if an automatic transfer switch is used.
Fix: Move the Run/Stop/Remote switch to the Remote position for automatic starting.
SHORT CIRCUIT — Shutdown 322
Cause: Indicates that generator output current has exceeded 175% of rated.
Fix: Contact an authorized service center.
RUPTURE BASIN — Warning 262
Cause: When any one of these customer defined inputs is closed to ground, the corresponding fault message is displayed. The nature of the fault is an optional customer selection. These fault functions can be programmed to initiate a shutdown or a warning. As indicated by the Warning lamp, a warning response has been preselected.
Fix: Note: Customer fault messages are editable. The message displayed for the code shown (260 thru 263) may have been edited and may not appear as shown in this table.
RUPTURE BASIN — Shutdown 262
Cause: When any one of these customer defined inputs is closed to ground, the corresponding fault message is displayed. The nature of the fault is an optional customer selection. These fault functions can be programmed to initiate a shutdown or a warning. As indicated by the Shutdown lamp, a shutdown response has been preselected.
Fix: Contact an authorized service center. Note: Customer fault messages are editable. The message displayed for the code shown (260 thru 263) may have been edited and may not appear as shown in this table.
RUN or fault lamp(s) does not light when Lamp Test switch is engaged.
Fix: Contact an authorized service center for assistance.
REVERSE POWER — Shutdown 335
Cause: Indicates improper CT or PT phasing. (Non-parallel units only.)
Fix: Contact an authorized service center.

Compiled from service & troubleshooting documentation across every generator set that uses the Cummins/Onan KTTA50-G2.

Maintenance schedule

Item	Spec	Capacity	Part #	Interval
Air filter	Maximum Air Cleaner Restriction, 25.0 in. H2O (6.2 kPa)		—
Fuel filter			—
Oil filter	Five spin-on, full flow		—
Battery			—	200 hr
Belt			—
Coolant		386.1 L	—	500 hr
Oil	Cummins	151.4 L	—	250 hr

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

Service intervals

Item	Action	Hours	Months	Notes
crankcase oil	Change	50 hr		First service — Drain and replace the crankcase oil after the first 50 hours of operation on new generator sets (break-in)
Crankcase oil and filter	Change	250 hr	12 mo	Standby applications: change oil every 12 months or 250 hours, whichever comes first
Generator bearing (P7 only)	Lubricate	4500 hr		Re-lubrication period 4000-4500 hours; 75 grams Kluber ASONIC GHY72
Rupture basin leak detect switch	Test		12 mo	Check once a year; in some areas weekly inspections may be required by safety code regulations

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	Air cleaner nozzle distance from element	at least 1 (25)	inch (mm)
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
Gap	MPU sensor to flywheel ring gear tooth	back it out one quarter turn	turn	sensor threaded in until it just touches gear tooth
Gap	Magnetic sensor air gap	.050- to .060-inch (1.27 to 1.52 mm)	inch (mm)
Other	AVR Droop setting	5	% at full load, 0 PF
Other	AVR voltage regulation (load regulation)	approximately ±0.5	% RMS
Other	Air cleaner element cleaning air pressure	30 (207)	psi (kPa)	low pressure compressed air through element from clean side
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	1.260		at 80°F
Other	Battery specific gravity (high ambient, above 95F/35C)	1.225		recommended to reduce electrolyte loss
Other	Battery specific gravity (recharge threshold)	below 1.260
Other	Battery specific gravity, fully charged	approximately 1.260	specific gravity	at 80 F (27 C)
Other	Continuous crank without cycle cranking option (PCC)	up to 75	seconds
Other	Cycle Cranker crank cycle time (A14-R4)	13- to 17-	seconds
Other	Cycle Cranker rest time (A14-R6)	8- to 12-	seconds
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	Low oil pressure / high engine temperature fault time delay after starter disconnect	about 10	seconds
Other	Maximum cranking voltage drop	2	volts	difference between battery and starter terminals while cranking
Other	Output frequency adjustment range	+/- 5	%	set running, not in idle mode
Other	Over/Under Frequency Sensor Module - Over Hz Set, 50 Hz nominal	55	Hz	reset 53 Hz
Other	Over/Under Frequency Sensor Module - Over Hz Set, 60 Hz nominal	65	Hz	reset 63 Hz
Other	Over/Under Frequency Sensor Module - Under Hz Set, 50 Hz nominal	45	Hz	reset 47 Hz
Other	Over/Under Frequency Sensor Module - Under Hz Set, 60 Hz nominal	55	Hz	reset 57 Hz
Other	Over/Under Voltage Sensor Module time delay	typically 25 percent, approximately 2.5	seconds
Other	Overcrank cranking limit	75	seconds	three 15-second cranking cycles with two 15-second rest periods
Other	Overcrank cranking limit (standard control)	75	seconds
Other	Overcrank cycle cranking (Detector, standard)	three 15-second cranking cycles with two 15-second rest periods	seconds
Other	Overcrank cycle cranking (PCC)	3, 4, or 5 cycles; crank and rest times 7 to 20	seconds
Other	Overcrank cycling option	three 15-second cranking cycles with two 15-second rest periods		12-lamp control
Other	Overcrank limit (Detector, optional)	75	seconds
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	Short circuit shutdown threshold	175% of rated	% of rated	generator output current
Other	Start delay (PCC, remote start in Auto)	0 to 300	seconds
Other	Start delay adjustment range	0 to 300	seconds
Other	Stop delay (PCC, remote stop in Auto)	0 to 600	seconds
Other	Stop delay adjustment range	0 to 600	seconds
Other	Time delay start (A15) adjustable	up to 15-	seconds
Other	Time delay stop (A15) adjustable	30-seconds to 5 minutes	minutes
Other	Under Frequency Roll Off (UFRO) knee point, 50 Hz units	48 to 49	Hz
Other	Under Frequency Roll Off (UFRO) knee point, 60 Hz units	58 to 59	Hz
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	Weak battery warning threshold	below 60% of nominal for two seconds	% of nominal	during starting
Pressure	Air cleaner element cleaning, compressed air pressure	30	psi (207 kPa)	blow through element from clean side; nozzle at least 1 inch (25 mm) away
Pressure	Detector oil pressure normal range after reset	25 to 40	psi (172 to 275 kPa)
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

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	water/antifreeze mixture (permanent type antifreeze)	Clean, low mineral content water free of chloride, sulphate or acid			Mix water and antifreeze per supplier recommendation for lowest expected ambient temperature; do not use antifreeze containing anti-leak additives
Engine oil	SAE 5W synthetic	API class CC/CD; sulphated ash content not exceeding 1.85 percent; pour point 9°F (5°C) below lowest expected temperature; viscosity 10,000 mPa.s maximum at -31°F (-35°C) and 4.1 mm2/s minimum at 212°F (100°C)	above -25°C		Recommended when ambient temperature is consistently below -13°F (-25°C) and there is no provision to keep the engine warm; do not use petroleum base 5W grade oil
Engine oil	multigrade / multiviscosity	API Class CC/CD; maximum sulphated ash content 1.85 percent	-25°C to 35°C		Specifications section lists ambient ranges -13°F to 95°F (-25°C to 35°C), 14°F (-10°C) and above, and 32°F (0°C) and above; single grade oil not recommended; do not mix oils of another classification or brand
Fuel	Diesel				Day tank fuel transfer pump maintains reservoir of diesel fuel in the day tank.
Fuel	No. 2 diesel				Engine will also operate on No. 1 fuel or other similar fuels if they meet certain specifications
Grease	Kluber, type ASONIC GHY72			75.0 grams	P7 generator bearing re-lubrication grease fill quantity; fill period 4000-4500 hours. Must not be mixed with any other type.
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	Molykote	Onan #524-0118			Apply a layer on the end-bell bearing bore before inserting bearing
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.
Other	Donaldsons D1400 solvent (or equivalent)				Air cleaner element cleaning: soak filter at least 15 minutes in water and Donaldsons D1400 solvent.

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	Engine operating in idle mode	Info	Remove ground from engine idle input to return to normal speed and voltage.
102	EMERGENCY STOP	Local or remote Emergency Stop activated	Shutdown	Pull button out or turn clockwise to pop out; move Run/Off/Auto switch to Off; press Reset; select Run or Auto. Reset only at PCC front panel.
200	LOW OIL PRESSURE	Engine oil pressure dropped to an unacceptable level	Warning	Follow 201 Low Oil Pressure procedure.
201	LOW OIL PRESSURE	Engine oil pressure below shutdown trip point	Shutdown	Check oil level, replenish if low, reset control and restart; contact authorized service center.
204	OIL PRES SENDER	Engine oil pressure sender not functioning correctly	Warning	Check sender connection; contact authorized service center.
210	LOW COOLANT TEMP	Engine coolant temperature 70 F (21 C) or lower	Warning	Check coolant heater power, fuse and cord; check coolant level and leaks.
211	HIGH COOLANT TEMP	Engine operating near cooling system capacity	Warning	Review 212 correction list; increase in load or higher ambient may cause shutdown.
212	HIGH COOLANT TEMP	Engine overheated; coolant above shutdown trip point	Shutdown	Cool engine; check coolant level, airflow obstructions and fan belt; reset and restart.
213	COOLANT SENDER	Resistance of coolant temperature sender out of range	Warning	Contact authorized service center.
214	LOW COOLANT LVL	Engine coolant level below trip point	Warning	Cool engine; check coolant level and leaks; reset control and restart.
215	LOW COOLANT LVL	Engine coolant level below trip point	Shutdown	Cool engine; check coolant level and leaks; reset control and restart. Shutdown will not occur in Idle mode.
220	MAG PICKUP	Mag pickup speed indication not sensed or does not match output frequency	Shutdown	Restart and check RPM on digital display; contact authorized service center.
221	FAIL TO CRANK	Possible fault with control or starting system	Shutdown	Clean and tighten battery cables; recharge or replace battery; contact service center.
222	OVERCRANK	Possible fuel system problem	Shutdown	Check fuel tank, leaks, plugged lines, fuel filter and air filter; reset control and restart.
223	OVERSPEED	Engine exceeded normal operating speed (2070 rpm @ 60 Hz; 1800 rpm @ 50 Hz)	Shutdown	Contact 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	Battery voltage below 24 VDC	Warning	Check battery charger fuse; recharge or replace battery; clean and tighten cable terminals.
231	HIGH DC VOLTAGE	Battery voltage exceeds 32 VDC	Warning	Contact authorized service center.
232	WEAK BATTERY	Battery voltage drops below 60% of nominal for two seconds during starting	Warning	See warning message 230 LOW DC VOLTAGE.
240	LOW FUEL - DAY	Day tank fuel supply running low	Warning	Check fuel supply and replenish as required.
241	LOW FUEL	Fuel supply running low	Warning	Check fuel supply and replenish as required.
250	EEPROM ERROR	PCC memory error; data corruption of critical operating parameters	Shutdown	Contact authorized service center.
251	EEPROM ERROR	PCC memory error; data corruption of noncritical operating parameters	Warning	Contact authorized service center.
252	EEPROM ERROR	PCC memory error; data corruption of noncritical operating parameters	Warning	Contact authorized service center.
260	CUSTOMER FAULT 1	Customer defined input closed to ground		Shutdown or warning preselected; message is editable; contact authorized service center.
261	GROUND FAULT	Customer defined input closed to ground		Shutdown or warning preselected; message is editable; contact authorized service center.
262	RUPTURE BASIN	Customer defined input closed to ground		Shutdown or warning preselected; message is editable; contact authorized service center.
263	HIGH GEN TEMP	Customer defined input closed to ground		Shutdown or warning preselected; message is editable; contact authorized service center.
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 110% of nominal for 10 seconds	Shutdown	Contact authorized service center.
303	LOW AC VOLTAGE	One or more phase voltages dropped below 85% of nominal for 10 seconds	Shutdown	Contact authorized service center.
313	UNDER FREQUENCY	Engine speed dropped below 90% of nominal for 10 seconds	Shutdown	Load Dump signal initiated five seconds before shutdown; contact authorized service center.
320	OVERCURRENT	Generator output current exceeded 110% of rated for 60 seconds	Warning	Contact authorized service center.
321	OVERCURRENT	Generator output current exceeded 110% of rated; PCC time/current calculation initiated shutdown	Shutdown	Contact authorized service center.
322	SHORT CIRCUIT	Generator output current exceeded 175% of rated	Shutdown	Contact authorized service center.
330	OVERLOAD	Three-phase power output exceeds 105% of standby (or 115% of prime) rating	Warning	Load Dump output activated after five seconds; warning activated after 60 seconds; contact authorized service center.
335	REVERSE POWER	Improper CT or PT phasing (non-parallel units only)	Shutdown	Contact authorized service center.
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.
FAULT 1	Fault 1 (Red)	Engine shut down because of a customer-connected system fault; part of a 10 second time delay shutdown circuit.	Shutdown	Service as required by the customer-supplied fault indicating switches.
FAULT 2	Fault 2 (Red)	Engine shut down because of a customer-connected system fault; part of a non-time delay shutdown circuit.	Shutdown	Service as required by the customer-supplied fault indicating switches.
GF	Ground Fault Alarm (Optional)	Ground fault relay monitors neutral to ground connection and line to neutral, activating a fault alarm when the connection is broken or a ground fault is sensed.	Warning	Clear fault condition by pushing the Run/Stop (Reset)/Remote switch to Reset (auto reset link set at factory).
HET	High Engine Temperature (Red)	Engine shut down because of excessively high engine coolant temperature (greater than 230 deg F).	Shutdown	Check coolant level and leaks; service cooling system; reset engine control.
HI ENG TEMP	High Engine Temperature	Engine shut down due to critically high coolant temperature (above 215F/102C).	Shutdown
High Engine Temperature	High Engine Temperature	On a five-light system, the High Engine Temperature switch connects to module A13-20; closure applies a ground which turns on A13-Q6 triggering A13-CR7 to conduct, providing a ground path for the fault light and to relay A11-K2 for engine shutdown. On single-light systems it is connected in parallel with low oil pressure to pin 4 of A12	Shutdown	Check coolant level, radiator cooling duct, fan belts, temperature sensor, thermostat and city water input solenoid valve
LET	Low Engine Temperature (Yellow)	Engine temperature is less than 70 deg F and the engine might not start.	Warning	Plug in, repair or install engine coolant and oil heaters.
LO FUEL	Low Fuel	Fuel supply is marginally low, if equipped (Detector-12).	Warning
LO OIL PRES	Low Oil Pressure	Engine shut down due to critically low oil pressure (below 14 psi/97 kPa).	Shutdown
LOP	Low Oil Pressure (Red)	Engine shut down because of excessively low engine oil pressure (less than 14 psi).	Shutdown	Check oil level and oil leaks; service lubricating system; reset engine control.
LOW ENG TEMP	Low Engine Temperature	Engine water jacket temperature is 70F/21C or lower; indicates possible inoperative coolant heater (Detector-12).	Warning
Low Engine Temperature	Low Engine Temperature	Closure of the Low Engine Temperature Sensing switch applies a ground to A13-8; A13-Q4 conducts and set-panel and remote Low Engine Temperature lights indicate a fault; there is no alarm or engine shutdown with this fault	Warning	Indicates a fault only; no shutdown or alarm
LOW FUEL	Low Fuel (Yellow)	Fuel level in the supply tank has dropped below the reserve necessary to run the set at full load for the prescribed number of hours.	Warning	Fill the main fuel supply tank with the appropriate grade of fuel.
Low Oil Pressure	Low Oil Pressure	Closure of the low oil pressure switch applies a ground to pin 4 of the A12 module; A12-Q4 turns on causing unijunction A12-Q7 to fire and trigger A12-CR6; fault light illuminates and on standard installations alarm and engine shutdown are initiated (Penn State sets alarm only). An adjustable rheostat A12-R11 provides a timed-delay up to 10 seconds	Shutdown	Check oil level and oil pressure sensor; disconnect wire from TB11-30 and check if light remains on
OC	Overcrank (Red)	Engine shut down because it did not start during the timed cranking period (approximately 75 seconds, including two rest periods).	Shutdown	Service the set as necessary; reset engine control.
OS	Overspeed (Red)	Engine shut down because of overspeed.	Shutdown	Adjust the Electronic Overspeed Module; check governor for binding; reset engine control.
OVERCRANK	Overcrank	Starter locked out because of excessive cranking time (limited to 75 seconds).	Shutdown
Overcrank	Overcrank	Engine fails to start after cranking for 75 seconds; capacitor A12-C1 on the Engine Monitor module charges to turn on A12-CR1, illuminates the fault light and applies a ground to pin 7 on A11 Engine Shutdown module which energizes A12-K1 allowing K12 to drop out and stop cranking	Shutdown	Check fuel system (valves open, tanks full) and ignition system; refer to engine manufacturer's troubleshooting
OVERSPEED	Overspeed	Engine shut down because of excessive speed.	Shutdown
Overspeed	Overspeed	Engine speed in excess of 2010 rpm causes transistor A16-Q2 on the Overspeed Sensor module to conduct and apply a ground to pin 2 of A12 Engine Monitor module; A12-Q8 turns on and triggers A12-CR8 to illuminate the fault light and initiate shutdown and alarm	Shutdown	Check throttles for freedom of movement and governor linkage; check injector rack movement; verify governor setting
PRE HI ENG TEMP	Pre-High Engine Temperature	Coolant temperature is marginally high (205F/97C or higher).	Warning	Attend to when generator set is shut down.
PRE LO OIL PRES	Pre-Low Oil Pressure	Engine oil pressure is marginally low (20 psi/138 kPa or less).	Warning	Attend to when generator set is shut down.
PRE-HET	Pre High Engine Temperature (Yellow)	Engine coolant temperature is abnormally high (greater than 220 deg F).	Warning	Shut down if possible or disconnect non-critical loads; service cooling system.
PRE-LOP	Pre Low Oil Pressure (Yellow)	Engine oil pressure is abnormally low (less than 20 psi).	Warning	Shut down if possible or disconnect non-critical loads; service lubricating system.
RUN	Run	Green lamp comes on when both primary and secondary starter circuits open after unit starts.	Info
SWITCH OFF	Switch-off (Flashing Red)	The Run/Stop/Remote switch is in the Stop position, preventing remote automatic operation.	Info	Push the Run-Stop-Remote switch to Remote.

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

Procedures

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 (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 (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.

Gain Adjustment adjustment

Close the main line circuit breaker and apply approximately 1/4 of the rated load.
Make sure the engine speed is constant.
Turn the GAIN potentiometer clockwise slowly until the engine speed is not constant.
Slowly turn the potentiometer counterclockwise until a constant speed is achieved, then an additional 1/2 division.

Governed Speed Adjustment adjustment

For 60 Hz full load, set engine no-load governed speed to 60.0 Hz (1800 RPM) isochronous, 61.8 Hz (1854 RPM) for 3% droop, or 63.0 Hz (1890 RPM) for 5% droop.
For 50 Hz full load, set engine no-load governed speed to 50.0 Hz (1500 RPM) isochronous, 51.5 Hz (1545 RPM) for 3% droop, or 52.5 Hz (1575 RPM) for 5% droop.
Use the SPEED ADJUST potentiometer on the engine instrument panel for fine speed adjustments of less than ±100 RPM.

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.

Preliminary Governor Adjustments adjustment

Idle Speed potentiometer: turn screw counterclockwise 20 turns then clockwise 10 turns to set mid position.
Run Speed potentiometer: turn screw counterclockwise 20 turns then clockwise 10 turns to set mid position.
Gain potentiometer: turn the screw fully counterclockwise.
Droop potentiometer: turn fully counterclockwise for isochronous operation; approximately 40 for 3 percent droop; approximately 80 for 5 percent droop.

Reconnection adjustment

Reconnect bus-bars for the different voltage per Figure 16
Reconnect lead from terminal 63 (inside control box) to either H3, H4 or H5
Select the proper tap on voltage reference transformer (T21) per Figure 2

Sensitivity Reference Circuit adjustment

Tools: Soldering iron

Solder wire W1 to terminal E1 for frequency sensitivity
Solder wire W1 to terminal E2 for non-frequency sensitivity

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).
	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.
110/190	3	Code 517		50 Hz; transformer tap H3
115/200	3	Code 517		50 Hz; transformer tap H4
120/208	3	Code 17		60 Hz; transformer tap H3
120/208	3	Code 517		50 Hz; transformer tap H4
120/240	3	Code 5D		Not reconnectible; frequency 60 Hz; transformer tap H5
127/220	3	Code 17		60 Hz; transformer tap H4
127/220	3	Code 517		50 Hz; transformer tap H5
139/240	3	Code 17		60 Hz; transformer tap H5
220/380	3	Code 517 / Code 7		50 Hz H3 and 60 Hz H3; transformer tap H3
230/400	3	Code 517		50 Hz; transformer tap H4
240/416	3	Code 517 / Code 17		50 Hz H4 and 60 Hz H3; transformer tap H4
240/480	3	Code 6D		Not reconnectible; frequency 60 Hz; transformer tap H5
254/440	3	Code 517 / Code 17		50 Hz and 60 Hz; transformer tap H5
277/480	3	Code 17		60 Hz; transformer tap H5
347/600	3	Code 9X		60 Hz; transformer tap H5
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 KTTA50 family

Part #	Description	Category
140-2503	Bracket, Mounting	Air filter
140-3163	Cleaner, Air (No Replaceable Element)	Air filter
140-3230	Cleaner, Air (Includes Elements - See Ref. No. 25 and 26)	Air filter
0300-4623-33	DFLE (600V)	Current transformer
0300-4623-57	DFLE BR (0-480V)	Current transformer
140-1260	Fitting, Safety Filter	Service part / kit
140-2395	Tube, Air Inlet	Service part / kit
140-2504-01	Bracket - Right Side	Service part / kit
140-2504-02	Bracket - Left Side	Service part / kit
140-2509	Tube, Air Inlet	Service part / kit
140-2528	Shield – Air In Heat	Service part / kit

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

Common questions

What is the oil capacity of the Cummins/Onan KTTA50-G2?

The Cummins/Onan KTTA50-G2 engine has an oil capacity of 151.4 liters.

What is the displacement of the Cummins/Onan KTTA50-G2?

The Cummins/Onan KTTA50-G2 has a displacement of 50.3 liters with 16 cylinders.

Which generators use the Cummins/Onan KTTA50-G2 engine?

The Cummins/Onan KTTA50-G2 powers 1 generator set(s), including Cummins/Onan DFM.

How often should you change the oil in the Cummins/Onan KTTA50-G2?

The Cummins/Onan KTTA50-G2 oil change interval is every 250 hours.

What is a common problem with the Cummins/Onan KTTA50-G2 engine?

A commonly reported issue on generators using the Cummins/Onan KTTA50-G2 is: LO OIL PRES lamp lights. Cause: Low coolant level. Fix: Check for low coolant level and replenish if required; look for possible coolant leakage points and repair as required.