Cummins/Onan 4.0 KY troubleshooting: 32 fault codes and 33 symptom-cause-remedy entries from the manufacturer's own service documentation.
Cummins/Onan 4.0 KY — full specs, parts & maintenance.
All Cummins/Onan fault codes →
| Code | Meaning | Cause | Remedy |
|---|---|---|---|
| 3 | Service Check — 3 flashes indicates a service fault (Code 3 fault); see second-level fault code | ||
| 4 | Over Crank — cranking exceeded 30 seconds without engine starting (4 flashes) | Cranking exceeded 30 seconds without engine starting | Check fuel level and fill the fuel tank if low; prime the engine fuel system by positioning the control switch to STOP/PRIME for 30 seconds; check and fill the LPG container as necessary; secure the spark plug lead(s) on the spark plug(s); replace the spark plug(s); replace the air filter if dirty; replace engine oil with oil of proper viscosity for the ambient temperature; tighten any fuel fitting if there is a fuel or air leak and reprime the engine fuel system; replace fuel filter |
| 12 | Over Voltage — Indicates the control is unable to maintain rated voltage | The control is unable to maintain rated voltage | Contact Local Dealer or Distributor |
| 13 | Under Voltage — Indicates the control is unable to maintain rated voltage | The control is unable to maintain rated voltage | Reduce the number of connected appliances, especially air conditioners and battery chargers (review load management in Loading the Generator Set) |
| 14 | Over Frequency — Indicates the engine governor is unable to maintain rated frequency | The engine governor is unable to maintain rated frequency | Contact Local Dealer or Distributor |
| 15 | Under Frequency — Indicates the engine governor is unable to maintain rated frequency | The engine governor is unable to maintain rated frequency | Reduce the number of connected appliances, especially air conditioners and battery chargers (review load management in Loading the Generator Set) |
| 27 | Voltage Sense — Indicates the control is unable to sense output voltage | The control is unable to sense output voltage | Contact Local Dealer or Distributor |
| 29 | High Battery Voltage — Indicates that voltage across the battery system is greater than 19 Volts | Voltage across the battery system is greater than 19 Volts | Check battery bank connections and reconnect if necessary so that the 12 Volt batteries serving the generator set are connected in parallel (12 Volt) rather than in series (24 Volt); select a lower battery boost charge rate |
| 32 | Low Cranking Speed — Indicates that cranking speed is less than 180 RPM for more than 2 seconds | Cranking speed is less than 180 RPM for more than 2 seconds | Clean and tighten the positive (+) and negative (–) battery cable connections at the battery and at the generator set; recharge or replace the battery; replace engine oil with oil of proper viscosity for the ambient temperature |
| 35 | Control Card Failure — Indicates that a microprocessor EEPROM error occurred during self test | A microprocessor EEPROM error occurred during self test | Contact Local Dealer or Distributor |
| 36 | Engine Stopped — Indicates that the engine stopped without receiving a command from the control | The engine stopped without receiving a command from the control | Check fuel level and fill the fuel tank if low; prime the engine fuel system by positioning the control switch to STOP/PRIME for 30 seconds; check and fill the LPG container as necessary; secure the spark plug lead(s) on the spark plug(s); replace the spark plug(s); replace the air filter if dirty; check for mechanical damage |
| 37 | Invalid Generator Set Configuration — Indicates that the frequency/RPM ratio is wrong | The frequency/RPM ratio is wrong | Contact Local Dealer or Distributor |
| 38 | Over Current (Field Overload) — Indicates low power factor loads | Low power factor loads | Reduce the number of connected appliances, especially air conditioners and battery chargers (review load management in Loading the Generator Set); have air conditioners and other appliances checked for proper operation |
| 41 | Generator Rotor — Indicates control is unable to sense field or output voltage | Control is unable to sense field or output voltage | Contact Local Dealer or Distributor |
| 42 | Processor — Indicates that a microprocessor ROM error occurred during self test | A microprocessor ROM error occurred during self test | Contact Local Dealer or Distributor |
| 43 | Processor — Indicates that a microprocessor RAM error occurred during self test | A microprocessor RAM error occurred during self test | Contact Local Dealer or Distributor |
| 45 | Speed Sense — Indicates the control is unable to sense quadrature frequency | The control is unable to sense quadrature frequency | Contact Local Dealer or Distributor |
| 47 | Ignition — Indicates the control is unable to sense ignition | The control is unable to sense ignition | Contact Local Dealer or Distributor |
| 48 | Generator Field Sense — Indicates the control is unable to sense field voltage | The control is unable to sense field voltage | Contact Local Dealer or Distributor |
| Code 27 | Indicates the control is unable to sense output voltage. | A. Contact Local Dealer or Distributor | |
| Code 29 | Indicates that voltage across the battery system is greater than 19 Volts. | A. Check Battery 1. Check battery bank connections and reconnect if necessary so that the 12 Volt batteries serving the generator set are connected in parallel (12 Volt) rather than in series (24 Volt). 2. Select a lower battery boost charge rate. | |
| Code 32 | Indicates that cranking speed is less than 180 RPM for more than 2 seconds. | A. Check Battery 1. Clean and tighten the positive (+) and negative (–) battery cable connections at the battery and at the generator set. 2. Recharge or replace the battery. Refer to the battery manufacturer's recommendations. B. Replace Engine Oil Replace engine oil with oil of proper viscosity for the ambient temperature. NOTICE: High oil viscosity can slow down cranking speed. | |
| Code 35 | Indicates that a microprocessor EEPROM error occurred during self test. | A. Contact Local Dealer or Distributor | |
| Code 36 | Indicates that the engine stopped without receiving a command from the control. | A. Check Fuel Level 1. If fuel level is low, fill the fuel tank. NOTICE: The generator set fuel pickup tube could be higher up in the fuel tank than the vehicle engine pickup. 2. Prime the engine fuel system by positioning the control switch to STOP/PRIME for 30 seconds. B. Check LPG Level Check and fill the LPG container, as necessary. NOTICE: On cold days, the LPG container may have to be kept at least half full to provide the rate of vaporization necessary to keep up with the generator set fuel demand. C. Check Spark Plug(s) 1. Secure the spark plug lead(s) on the spark plug(s). 2. Replace the spark plug(s). | |
| Code 37 | Indicates that the frequency/RPM ratio is wrong. | A. Contact Local Dealer or Distributor | |
| Code 38 | Indicates low power factor loads. | A. Reduce Load Reduce the number of connected appliances, especially air conditioners and battery chargers. (Review load management in Loading the Generator Set.) B. Check Appliances for Proper Operation Have air conditioners and other appliances checked for proper operation. | |
| Code 41 | Indicates control is unable to sense field or output voltage. | A. Contact Local Dealer or Distributor | |
| Code 42 | Indicates that a microprocessor ROM error occurred during self test. | A. Contact Local Dealer or Distributor | |
| Code 43 | Indicates that a microprocessor RAM error occurred during self test. | A. Contact Local Dealer or Distributor | |
| Code 45 | Indicates the control is unable to sense quadrature frequency. | A. Contact Local Dealer or Distributor | |
| Code 47 | Indicates the control is unable to sense ignition. | A. Contact Local Dealer or Distributor | |
| Code 48 | Indicates the control is unable to sense field voltage. | A. Contact Local Dealer or Distributor |
| Symptom | Cause | Remedy |
|---|---|---|
| Status Indicator Not Working — Indicates that there could be faulty connections or no battery voltage | Faulty connections or no battery voltage | Try the generator set control switch if the remote control switch start doesn't work, and vice versa; clean and tighten the positive (+) and negative (–) battery cable connections at the battery and at the generator set; recharge or replace the battery |
| Starting Batteries Run Down — Indicates problem with batteries, connections, charging system, or parasitic loads | Problem with batteries, connections, charging system, or parasitic loads | Clean and tighten the positive (+) and negative (–) battery cable connections at the battery and at the generator set; recharge or replace the battery; install or service a battery charging system in the vehicle |
| Starter Engages-Disengages — Indicates cranking voltage dips below 6 Volts | Cranking voltage dips below 6 Volts | Run the vehicle propulsion engine while trying to start the generator set—the battery charging alternator may be able to maintain starting voltage high enough to start the generator set; clean and tighten the positive (+) and negative (–) battery cable connections at the battery and at the generator set; recharge or replace the battery; increase battery cable size or run parallel cables |
| Status Indicator Goes Out While Cranking—No Start — Indicates an internal short circuit caused an automatic-reset circuit protective device to trip | An internal short circuit caused an automatic-reset circuit protective device to trip | If the status indicator flashes and goes out again without the engine starting, call local dealer or distributor |
| No Power—Generator Set Running, Status Light On — Indicates line circuit breaker is OFF, or tripped due to short circuit or overload | Line circuit breaker is OFF, or tripped due to short circuit or overload | Turn on or reset the line circuit breaker on the generator set; turn on or reset the line circuit breaker on the main distribution panel in the vehicle |
| The engine fails to crank | Try starting at the genset rather than at the remote control | |
| The engine cranks slowly | Disconnect the air conditioner and other large loads | |
| The engine cranks but fails to start | Check the fuel tank and fill if necessary | |
| The engine runs and then stops or surges | Check the fuel tank and fill if necessary | |
| The genset keeps stalling or the circuit breaker keeps tripping | Try running with fewer appliances connected. See Powering Equipment | |
| There is no electrical power even though the genset runs | Reset tripped circuit breakers. See Powering Equipment | |
| The engine fails to crank | Fuse on the control panel has blown | Replace the fuse on the control panel if it has blown |
| The engine fails to crank | Loose or dirty battery cable connections | Clean and tighten the positive (+) and negative (-) battery cable connections at the battery and the genset |
| The engine fails to crank | Battery discharged | Recharge the battery. Refer to the battery manufacturer's recommendations |
| The engine cranks slowly | Large electrical loads connected | Disconnect the air conditioner and other large loads |
| The engine cranks slowly | Loose or dirty battery cable connections | Clean and tighten the positive (+) and negative (-) battery cable connections at the battery and the genset |
| The engine cranks slowly | Battery discharged | Recharge the battery. Refer to the battery manufacturer's recommendations |
| The engine cranks slowly | Engine oil viscosity not proper for ambient temperature | Change the engine oil to oil having the proper viscosity for the ambient temperature. See Table 1 |
| The engine cranks but fails to start | Fuel tank empty | Check the fuel tank and fill if necessary |
| The engine cranks but fails to start | Closed fuel shut off valve | Open any closed fuel shut off valve |
| The engine cranks but fails to start | Low engine oil level | Check engine oil level and add oil as necessary |
| The engine cranks but fails to start | Air cleaner dirty | Service the air cleaner |
| The engine cranks but fails to start | Spark plug lead not secure | Secure the spark plug lead on the spark plug |
| The engine cranks but fails to start | Faulty spark plug | Replace the spark plug |
| The engine runs and then stops or surges | Fuel tank empty | Check the fuel tank and fill if necessary |
| The engine runs and then stops or surges | Engine oil level incorrect | Check the engine oil level and add oil as necessary. Drain excess oil if the level is above the dipstick Full mark |
| The engine runs and then stops or surges | Carburetor altitude adjust knob not set correctly (gasoline models only) | Check and reset the carburetor altitude adjust knob. See Varying Operating Conditions. (Gasoline models only.) |
| The engine runs and then stops or surges | Spark plug lead not secure | Secure the spark plug lead on the spark plug |
| The engine runs and then stops or surges | Faulty spark plug | Replace the spark plug |
| The genset keeps stalling or the circuit breaker keeps tripping | Too many appliances connected | Try running with fewer appliances connected. See Powering Equipment |
| The genset keeps stalling or the circuit breaker keeps tripping | Low LPG level (LPG models); on cold days the LPG container may have to be kept at least half full to provide the rate of vaporization necessary to keep up with the genset fuel demand | Check the fuel tank (LPG models) and fill as necessary |
| There is no electrical power even though the genset runs | Tripped circuit breakers | Reset tripped circuit breakers. See Powering Equipment |
| There is no electrical power even though the genset runs | Vehicle power cord not plugged into the genset power output receptacle or vehicle power selector not turned | Unless there is an automatic power transfer switch, plug the vehicle power cord into the genset power output receptacle (if so equipped) or turn the vehicle power selector |
Fault codes and symptom→remedy steps extracted from this model’s service/owner documentation; verify against the official manual before servicing.
Documented causes: Fuel tank empty; Closed fuel shut off valve; Low engine oil level; Air cleaner dirty. See the table for the matching fixes.
Documented causes: Fuel tank empty; Engine oil level incorrect; Carburetor altitude adjust knob not set correctly (gasoline models only); Spark plug lead not secure. See the table for the matching fixes.
Documented causes: Large electrical loads connected; Loose or dirty battery cable connections; Battery discharged; Engine oil viscosity not proper for ambient temperature. See the table for the matching fixes.