Cummins/Onan G855 Series Engine troubleshooting: 26 fault codes and symptom-cause-remedy entries from the manufacturer's own service documentation.
Cummins/Onan G855 Series Engine — full specs, parts & maintenance.
All Cummins/Onan fault codes →
| Code | Meaning |
|---|---|
| TS-6 | Engine Decelerates SIOWLY |
| TS-7 | Engine Difficult to Start or Will Not Start |
| TS-8 | Engine Noise ExCeSSive |
| TS-9 | Engine Power Output LOW |
| TS-10 | Engine RUns Rough at Idle |
| TS-11 | Engine Runs Rough or Misfires |
| TS-12 | Engine Speed Surges at Low or High Idlle |
| TS-13 | Engine Starts But Will Not Keep RUNMNING |
| TS-14 | Engine Transient RESPONSE POOM |
| TS-15 | Engine Vibration ExCessive |
| TS-17 | Engine Will Not Crank or Cranks Slowly (Air Starter) |
| Symptom | Cause | Remedy |
|---|---|---|
| Engine Will Not Reach Rated Speed (RPM) | Low or no fuel pressure at the mixer (secondary pressure) | Increase output pressure from the secondary regulator. |
| Engine Will Not Shut Off | Stop/Run switch circuit is malfunctioning, Engine is running on fumes drawn into the air intake | Check the Stop/Run switch circuit. Refer to the OEM service manual. Check the air intake ducts. Locate and isolate the source of the fumes. Repair as necessary. Refer to the OEM installation and service manual. |
| Lubricating Oil Consumption Excessive | External oil leaks, Lubricating oil level is above or below specification, Lubricating oil does not meet specifications for operating conditions, Engine is cold (Coolant Temperature Below Normal) | Inspect the engine for external oil leaks. Tighten the capscrews, pipe plugs, and fittings. Replace gaskets, if necessary. Refer to Procedure 018-009 (Capscrew Markings and Torque Values) in Section V torque for specifications. Check the oil level. Add or drain oil, if necessary. Refer to Procedure 007-043 (Lubricating Oil Level) in Section 3 and Procedure 007-002 (Lubricating Oil and Filters) in Section 4. Allow the engine to warm to operating temperature. If the engine will not reach operating temperature, refer to the Coolant Temperature Below Normal symptom tree. Change the oil and filters. Refer to Procedure 007-002 (Lubricating Oil and Filters) in Section 4. Use the oil recommended in Section V. Contact a Cummins Authorized Repair Facility. |
| Lubricating Oil Pressure High | Lubricating oil pressure switch, gauge, or sensor is malfunctioning or is not in the correct location | Check the oil pressure switch, gauge, or sensor for correct operation and location. Refer tothe OEM service manual. Refer to the Coolant Temperature Below Normal symptom tree. Change the oil and filters. Refer to Procedure 007-002 (Lubricating Oil and Filters) in Section 4. Use the oil type recommended in Section V. |
| Lubricating Oil Pressure Low | Lubricating oil level is above or below specification, Lubricating oil pressure switch, gauge, or sensor is malfunctioning or is not in the correct location | Check the oil level. Add or drain oil if necessary. Refer to Procedure 007-043 (Lubricating Oil Level) in Section 3 and Procedure 007-002 (Lubricating Oil and Filters) in Section 4. Check the dipstick calibration. Check the oil pressure switch, gauge, or sensor for correct operation and location. Refer tothe OEM service manual. |
| Coolant Loss - External | Radiator cap is not correct, is malfunctioning, or has low-pressure rating | Check the radiator pressure cap. Refer to the OEM service manual. |
| Coolant Temperature Above Normal - Gradual Overheat | Coolant level is below specification; Lubricating oil level is above or below specification; Load is excessive for engine horsepower rating; Coolant temperature gauge is malfunctioning; Radiator fins are damaged or obstructed with debris; Radiator cap is not correct, is malfunctioning, or has low-pressure rating; Cooling system hose is collapsed, restricted, or leaking | Inspect the engine and cooling system for external coolant leaks. Repair if necessary. Add coolant.; Beene enannne Check the oil level. Add or drain oil, if necessary.; Refer to Procedure 007-043 (Lubricating Oil Level) in Sections 3 and Procedure 007-002 (Lubricating Oil and Filters) in Section 4.; Reduce the load on the engine. Refer to OEM specifications.; Test the temperature gauge. Repair or replace the gauge if necessary. Refer to the OEM service manual.; Inspect the radiator fins. Clean and repair the fins as necessary. Refer to the OEM service manual.; Check the radiator pressure cap. Refer to the OEM service manual. |
| Coolant Temperature Below Normal | Engine is operating at low ambient temperature | OK |
| Engine Decelerates Slowly | Compare the calibration in the electronic control system with the engine rating and the Control Parts Electronic control module system calibration is |............ List (CPL), Bulletin number 3379133 or 4021327. If not correct necessary, calibrate the system. | Refer to a Cummins Authorized Repair Facility. |
| Throttle plate is malfunctioning | Refer to a Cummins Authorized Repair Facility. | |
| Engine cranking speed is slower than 150 rpm | Refer to the Engine Will Not Crank or Cranks Slowly symptom tree. | |
| Air intake system restriction | STEP 3 Air intake system restriction is above specification | Replace the air filter. Refer to Procedure 010-059 (Air Cleaner Restriction) in Section 4 and Procedure 010-060 (Air Cleaner Element, Single Heavy Duty Dry Type) in Section 6. |
| Engine-driven units are engaged | Disengage engine-driven units. Verify the correct starting procedure. Refer to Procedure 101-014 (Normal Starting Procedure) in Section 1. | |
| Engine cranking speed is too slow | Inspect the air intake system for restriction. Replace the air filter. Refer to Procedure 010-059 (Air Cleaner Restriction) in Section 4 and Procedure 010-060 (Air Cleaner Element, Single Heavy Duty Dry Type) in Section 6. | |
| Engine Starts But Will Not Keep Running | Fuel valve closed (Manual), Load is excessive for engine horsepower rating, Air intake system restriction is above specification, Exhaust system resiriction is not within specification, Fuel supply pressure is below specification, Low or no fuel pressure at the mixer (secondary pressure) | Inspect the air intake system for restriction. Check the exhaust system for restrictions. Measure the fuel supply pressure. |
Fault codes and symptom→remedy steps extracted from this model’s service/owner documentation; verify against the official manual before servicing.
Documented causes: Low or no fuel pressure at the mixer (secondary pressure). See the table for the matching fixes.
Documented causes: Stop/Run switch circuit is malfunctioning, Engine is running on fumes drawn into the air intake. See the table for the matching fixes.
Documented causes: External oil leaks, Lubricating oil level is above or below specification, Lubricating oil does not meet specifications for operating conditions, Engine is cold (Coolant Temperature Below Normal). See the table for the matching fixes.