Onan QG 5500 generator fault codes
Reviewed 2 primary sourcesSee sources
The QG 5500 flashes 2 for low oil pressure, 3 for a service fault and 4 for overcrank. Press STOP/PRIME once after a 3 to read the two-digit code.
Cummins Onan · RV generator · QG 5500 (HGJAB). Models: HGJAB Spec J–L, HGJAA Spec J–K.
Cummins’s QG 5500 spec sheet lists the HGJAB models and names operator manual A035D009. The same manual covers HGJAA, whose sales name we could not confirm.[2]
How to read the code
After a shutdown the status light flashes 2 for low oil pressure, 3 for a service fault or 4 for overcrank. After a 3, press STOP/PRIME once to see the two-digit code. Rapid continuous flashing means Engine Run Only mode with AC output off.[1]
Codes: HGJAA Spec J–K and HGJAB Spec J–L
| Code | Meaning | What to do | Who fixes it |
|---|---|---|---|
| 2 | Low oil pressure: cutoff switch did not open. | Check dipstick: add oil if low; drain excess if above full.[1] | Owner check |
| 3 | Service check: see second-level code. | Press STOP/PRIME once to see the two-digit code.[1] | Check, then service if it persists |
| 4 | Over crank: cranking exceeded 30 s without starting. | Fill fuel tank if low and prime at STOP/PRIME 30 s; LPG: fill container (half full on cold days); secure/replace spark plugs; replace dirty air filter. Correct oil viscosity; fix leaking fuel fittings and reprime; replace fuel filter.[1] | Check, then service if it persists |
| 12 | Over voltage. | Not an owner fix. Contact a Cummins Onan dealer or distributor.[1] | Technician |
| 13 | Under voltage. | Reduce connected appliances.[1] | Owner check |
| 14 | Over frequency. | Not an owner fix. Contact a Cummins Onan dealer or distributor.[1] | Technician |
| 15 | Under frequency. | Reduce connected appliances.[1] | Owner check |
| 19 | Governor actuator: open or shorted circuit. | Not an owner fix. Contact a Cummins Onan dealer or distributor.[1] | Technician |
| 22 | Governor actuator overload: running near full duty cycle beyond design limit. | Reduce load; replace dirty air filter; remove exhaust blockage.[1] | Owner check |
| 27 | Voltage sense. | Not an owner fix. Contact a Cummins Onan dealer or distributor.[1] | Technician |
| 29 | High battery voltage: over 19 V. | Batteries in parallel (12 V), not series; lower charge rate.[1] | Owner check |
| 31 | Over speed: engine over 3400 RPM. | Not an owner fix. Contact a Cummins Onan dealer or distributor.[1] | Technician |
| 32 | Low cranking speed: under 180 RPM over 2 s. | Clean and tighten the battery connections, recharge or replace the battery, and make sure the oil is the right viscosity.[1] | Owner check |
| 35 | Control card failure: EEPROM self-test error. | Not an owner fix. Contact a Cummins Onan dealer or distributor.[1] | Technician |
| 36 | Engine stopped without command from control. | Fill fuel tank if low and prime at STOP/PRIME 30 s; LPG: fill container (half full on cold days); secure/replace spark plugs; replace dirty air filter. Check for mechanical damage.[1] | Check, then service if it persists |
| 37 | Invalid generator set configuration: frequency/RPM ratio wrong. | Not an owner fix. Contact a Cummins Onan dealer or distributor.[1] | Technician |
| 38 | Over current (field overload): low power factor loads. | Reduce load; have appliances checked.[1] | Check, then service if it persists |
| 41 | Generator rotor. | Not an owner fix. Contact a Cummins Onan dealer or distributor.[1] | Technician |
| 42 | Processor: ROM self-test error. | Not an owner fix. Contact a Cummins Onan dealer or distributor.[1] | Technician |
| 43 | Processor: RAM self-test error. | Not an owner fix. Contact a Cummins Onan dealer or distributor.[1] | Technician |
| 45 | Speed sense. | Not an owner fix. Contact a Cummins Onan dealer or distributor.[1] | Technician |
| 47 | Ignition. | Not an owner fix. Contact a Cummins Onan dealer or distributor.[1] | Technician |
| 48 | Generator field sense. | Not an owner fix. Contact a Cummins Onan dealer or distributor.[1] | Technician |
| 51 | Processor: microprocessor malfunction. | Not an owner fix. Contact a Cummins Onan dealer or distributor.[1] | Technician |
| 52 | Fuel injector open or short circuit. | Not an owner fix. Contact a Cummins Onan dealer or distributor.[1] | Technician |
| 54 | MAT sender open or short circuit. | Not an owner fix. Contact a Cummins Onan dealer or distributor.[1] | Technician |
| 56 | MAP sender open or short circuit. | Not an owner fix. Contact a Cummins Onan dealer or distributor.[1] | Technician |
| 57 | Over prime: priming exceeded 3 minutes. | Remove any object holding a control switch (remote or generator) in STOP/PRIME.[1] | Owner check |
| 58 | Exhaust gas temperature shutdown: 650 C (1202 F) for 2 s while running. | Not an owner fix. Contact a Cummins Onan dealer or distributor.[1] | Technician |
| 81 | EGT sensor open (below 60 C/140 F for 2 min while running, or not above it within 2 min of start). | Not an owner fix. Contact a Cummins Onan dealer or distributor.[1] | Technician |
| 82 | EGT sensor shorted (reads 1000 C/1832 F for 1 s). | Not an owner fix. Contact a Cummins Onan dealer or distributor.[1] | Technician |
| High-frequency flashing | Operating in Engine Run Only (ERO) mode; AC output disabled. | The manual gives no owner action.[1] | Check, then service if it persists |
When to call a technician
Codes marked as service items need an authorized Cummins Onan dealer; the manual reserves deeper fault-finding for trained technicians.[1] Our mobile RV repair listings cover Colorado Springs and the Boise area so far.
Sources
Facts on this page are restated from the manufacturer documents below. Codes differ by model and spec letter, so check the manual for your exact unit. We have not tested these codes on equipment.
- Operator Manual - Onan Generator Set for RV, HGJAA (Spec J-K), HGJAB (Spec J-L)Cummins Inc. (Onan) · A035D009 · Safety section 1; fault codes section 6.2 · retrieved
- RV QG 5500 specification sheetCummins Inc. (Onan) · PDA-1425 · Model list and operation manual reference · retrieved
Primary publishers: Cummins Inc. (Onan). Spotted an error? Email the address in the footer with the model and the document you are using.