Cummins/Onan 3.6KY troubleshooting: 60 fault codes and 12 symptom-cause-remedy entries from the manufacturer's own service documentation.
Cummins/Onan 3.6KY — full specs, parts & maintenance.
All Cummins/Onan fault codes →
| Code | Meaning | Cause | Remedy |
|---|---|---|---|
| 3 | Service check fault — First-level fault code—Indicates fault with second-level fault code | Check the second-level fault code by pressing STOP once. The second-level fault code will have two-digits. The faults are listed in numerical order in this table. | |
| 4 | Overcrank fault — First-level fault code—Cranking exceeded 20 seconds without engine starting | Gasoline Models − Check and fill the fuel tank, as necessary. (Note: The genset fuel pickup tube is probably higher up in the fuel tank than the vehicle engine pickup.); Prime the engine fuel system by holding the control switch at Stop/Prime for 30 seconds; LPG Models − Check and fill the LPG container, as necessary. 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; Open any closed fuel valves; Secure the spark plug lead on the spark plug (Page 3-6); Replace the spark plug (Page 3-6); Service the air cleaner (Page 3-5). | |
| 12 | Overvoltage fault — Controller unable to maintain rated voltage | See an authorized Onan dealer. | |
| 13 | Undervoltage fault — Controller unable to maintain rated voltage | Reduce the number of connected appliances, especially when air conditioners and battery chargers are running. | |
| 14 | Overfrequency fault — Engine governor unable to maintain rated frequency | See an authorized Onan dealer. | |
| 15 | Underfrequency fault — Engine governor unable to maintain rated frequency | Reduce the number of connected appliances, especially when air conditioners and battery chargers are running. | |
| 27 | Voltage sense fault — Controller unable to sense output voltage | See an authorized Onan dealer. | |
| 29 | High battery voltage fault — Voltage across battery system greater than 19 volts | Check battery bank connections and reconnect if necessary so that the 12 volt batteries serving the genset are connected in parallel (12 volt) rather than in series (24 volt); Select a lower battery boost charge rate. | |
| 32 | Low cranking speed fault — Cranking speed 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 genset; Recharge or replace the battery. Refer to the battery manufacturer's recommendations; Replace engine oil with oil of proper viscosity for ambient temperatures (Page 1-3). (High oil viscosity can slow down cranking speed.) | |
| 35 | Control card failure fault — Microprocessor EEPROM error during self-test | See an authorized Onan dealer. | |
| 36 | Engine stopped fault — Engine stopped without command by controller | Gasoline Models − Check and fill the fuel tank, as necessary. (Note: The genset fuel pickup tube is probably higher up in the fuel tank than the vehicle engine pickup.); LPG Models − Check and fill the LPG container, as necessary. 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; Secure the spark plug lead on the spark plug (Page 3-6); Replace the spark plug (Page 3-6); Service the air cleaner (Page 3-5); Check for mechanical damage. | |
| 37 | Invalid genset configuration fault — Genset configuration is preprogrammed at the factory | See an authorized Onan dealer. | |
| 38 | Overcurrent fault — Low power factor loads | Reduce the number of appliances running at the same time, especially those with high motor starting loads such as air conditioners; Have air conditioners and other appliances checked for proper operation. (A locked compressor rotor can cause very low power factor.) | |
| 41 | Generator rotor fault — Controller unable to sense field or output voltage | See an authorized Onan dealer. | |
| 42 | Processor fault — Microprocessor ROM error during self-test | See an authorized Onan dealer. | |
| 43 | Processor fault — Microprocessor RAM error during self-test | See an authorized Onan dealer. | |
| 45 | Speed sense fault — Controller unable to sense quadrature frequency | See an authorized Onan dealer. | |
| 47 | Ignition fault — Controller unable to sense ignition | See an authorized Onan dealer. | |
| 48 | Generator field sense fault — Controller unable to sense field voltage | See an authorized Onan dealer. | |
| CODE NO. 38 | OVERCURRENT FAULT—Low power factor loads | 1. Reduce the number of appliances running at the same time, especially those with high motor starting loads such as air conditioners. 2. Have air conditioners and other appliances checked for proper operation. (A locked compressor rotor can cause very low power factor.) | |
| CODE NO. 41 | GENERATOR ROTOR FAULT—Controller unable to sense field or output voltage | See an authorized Onan dealer. | |
| CODE NO. 42 | PROCESSOR FAULT—Microprocessor ROM error during self-test | See an authorized Onan dealer. | |
| CODE NO. 43 | PROCESSOR FAULT—Microprocessor RAM error during self-test | See an authorized Onan dealer. | |
| CODE NO. 45 | SPEED SENSE FAULT—Controller unable to sense quadrature frequency | See an authorized Onan dealer. | |
| CODE NO. 47 | IGNITION FAULT—Controller unable to sense ignition | See an authorized Onan dealer. | |
| CODE NO. 48 | GENERATOR FIELD SENSE FAULT—Controller unable to sense field voltage | See an authorized Onan dealer. | |
| 3 | Service check fault | Any Two-Digit Fault Code | Verify that Last Fault is FC 3: Yes, continue diagnosis; No, troubleshoot actual last fault; While LED is flashing three times press stop once (1 second duration): trouble shoot Two-Digit Fault Code |
| 4 | Overcrank | ||
| 12 | Overvoltage | ||
| 13 | Undervoltage | ||
| 14 | Overfrequency | ||
| 15 | Underfrequency | ||
| 27 | Voltage Sense Lost | ||
| 29 | High Battery Voltage | ||
| 32 | Low Cranking Speed Sense | ||
| 33 | Fault Code 33 | ||
| 35 | Control Card Failure | ||
| 36 | Genset Stopped Without Fault Condition | ||
| 38 | Field Overload (Overvoltage) | ||
| 41 | Generator Rotor Fault | ||
| 42 | Processor Fault | ||
| 43 | Processor Fault | ||
| 45 | Speed Sense Fault | ||
| 48 | Field Sense Fault | ||
| 51 | Processor Failure | ||
| 4 | Overcrank — Controller unable to sense genset frequency after 20 seconds of holding start switch | Faulty switch, faulty external start command, fuel supply, air fuel mixture, exhaust system, wire connections, starter, ignition system | Verify that Last Fault is FC 4: Yes, continue diagnosis; No, troubleshoot actual last fault; Measure for continuity change across start/stop switch between neutral and start position at switches and P1 connector: replace switches as necessary or disconnect external start device if so equipped; Disconnect genset control P1 connector |
| 12 | High AC voltage — Instantaneous Fault – AC voltage S1–S2 greater than 150 VAC; Delayed Fault – AC voltage S1–S2 greater than 138 VAC, but less than 150 VAC for 3 continuous minutes | Genset loads, Inverter/Charger, wire connections, AC sense transformer, windings | Verify that Last Fault is FC 12: Yes, continue diagnosis; No, troubleshoot actual last fault; Measure AC voltage; Measure AC frequency while changing engine rpm to determine if frequency response matches engine rpm response: repair damaged generator drive system as necessary; Cycle loads to determine if a particular load causes fault: diagnose faulty load as necessary; Determine Inverter/Charger battery charge rate (typical default is 80 percent): if adjustable reduce to 30 percent; Verify balanced loads in 120/240 VAC applications: balance loads within 10 percent line–to–line as required; If the genset will not stay running measure genset frequency, quadrature winding and main winding voltages using Break-Out Tool 420–0603 and Instruction Sheet R1098; Remove connector P1 from control and re-install and try to start genset: inspect, repair or replace P1 connector pins as necessary; Measure field, quadrature and main winding resistance: clean slip rings, replace brushes, repair harness and replace rotor or stator as necessary; Measure field, quadrature and main winding resistance to ground: clean slip rings, replace brushes, repair harness and replace rotor or stator as necessary; Measure field, quadrature and main winding resistance to each other: clean slip rings, replace brushes, repair harness and replace rotor or stator as necessary; Check brush alignment per PSB-682a; Dealers contact Distributor for technical support, Distributors contact factory for technical support |
| 13 | Undervoltage — AC voltage S1–S2 less than 108 VAC for 5 continuous seconds | Genset loads, Inverter/Charger, wire connections, generator drive system, windings, AC sense transformer, windings | Verify that Last Fault is FC 13: Yes, continue diagnosis; No, troubleshoot actual last fault; Measure AC voltage; Measure AC voltage in and out of sense transformer (if so equipped): repair wire connection, replace sense transformer as necessary; Measure AC frequency while changing engine rpm to determine if frequency response matches engine rpm response: repair damaged generator drive system as necessary; Cycle loads to determine if a particular load will cause fault: diagnose faulty load as necessary; Determine battery charge rate (typical default is 80 percent): if adjustable reduce to 30 percent; Verify balanced loads in 120/240 VAC applications: balance loads within 10 percent line–to–line as required; If the genset will not stay running measure genset frequency, quadrature winding and main winding voltages using Break-Out Tool 420–0603 and Instruction Sheet R1098; Remove connector P1 from control and re-install and try to start genset: inspect, repair or replace P1 connector pins as necessary; Measure field, quadrature and main winding resistance: clean slip rings, replace brushes, repair harness and replace rotor or stator as necessary; Measure field, quadrature and main winding resistance to ground: clean slip rings, replace brushes, repair harness and replace rotor or stator as necessary; Measure field, quadrature and main winding resistance to each other: clean slip rings, replace brushes, repair harness and replace rotor or stator as necessary; Check brush alignment per PSB-682a; Dealers contact Distributor for technical support, Distributors contact factory for technical support |
| 14 | Overfrequency — Instantaneous Fault – Frequency greater than 70Hz; Delayed Fault – Frequency greater than 66Hz, but less than 70Hz, for 3 continuous seconds | Genset loads, Inverter/Charger, engine governor function, fuel supply, air fuel mixture, exhaust system, choke, demand regulator, carburetor, generator drive system, generator windings, ignition, wire connections | Verify that Last Fault is FC 14: Yes, continue diagnosis; No, troubleshoot actual last fault; Measure AC current while running genset with vehicle loads: identify faulty or short cycling loads; Determine battery charge rate (typical default is 80 percent): if adjustable reduce to 30 percent; Measure genset load capability with shop load bank (derate for altitude and temperature as necessary); Measure genset frequency and droop while running; Measure AC frequency while changing engine rpm to determine if frequency response matches engine rpm response: repair damaged generator drive system as necessary; Disconnect genset control P1 connector, verify P1 pins are fully inserted and inspect pin condition per PSB–676: insert, repair or replace pins as necessary; Reconnect P1 connector and test run genset for fault occurrence: repair or replace pins in connector as necessary; Check all grounds and neutral leads for looseness at battery, genset, inverter/converter; run genset on separate battery: tighten or replace terminals and leads as necessary; Check air filter cleanliness; replace air filter as necessary; Check for blocked or damaged exhaust system: repair or replace exhaust components as necessary; If the genset will not stay running measure genset frequency, quadrature winding and main winding voltages using Break-Out Tool 420–0603 and Instruction Sheet R1098; Gasoline Models: Vapor lock may occur in high ambient temperatures: operate in ambients at less than 120°F; verify proper installation to prevent air recirculation; correct as necessary; Verify steady DC voltage at fuel pump while genset is running; repair wiring as necessary; Run genset on shop fuel supply; verify tank level and fuel line condition in vehicle; Verify carburetor altitude setting; readjust as necessary; Verify choke operation, setting and linkage damage; readjust, repair or replace as necessary; Measure throttle stop frequency; readjust as necessary; Measure fuel pump pressure/flow: replace fuel filter or pump as necessary; Propane Models: When ambient temperatures are less than 40°F, vapor-withdrawal Propane tanks should be at least half full to provide proper vaporization rate; Propane having more than 2.5 percent Butane will not vaporize in ambients at less than 32°F; use HD–5 grade Propane; Verify steady DC voltage at fuel solenoid and priming solenoid (if so equipped) while genset is running; repair wiring as necessary; Verify clear vent hose; Run genset on shop fuel supply; verify tank level and fuel line condition in vehicle; Measure throttle stop frequency; readjust as necessary; Check genset fuel lines for damage: replace fuel line as required; Measure regulator lock off pressure; Verify priming solenoid operation, if so equipped; Check governor, actuator, linkage and spring for debris, damage and looseness: readjust and repair as necessary; Measure field, quadrature and main winding resistance: clean slip rings, replace brushes, repair harness and replace rotor or stator as necessary; Measure field, quadrature and main winding resistance to ground: clean slip rings, replace brushes, repair harness and replace rotor or stator as necessary; Measure field, quadrature and main winding resistance to each other: clean slip rings, replace brushes, repair harness and replace rotor or stator as necessary; Check brush alignment per PSB-682a; Verify that spark plug cable is secure on spark plug: reconnect or replace as necessary; Inspect ignition kill lead in harness and at connector P1: repair or replace lead, terminal or pins as necessary; Test magneto: Disconnect Connector P1; Connect positive(+) meter lead to chassis ground; Measure continuity to negative lead at pin P1–15: replace magneto as necessary; Measure spark plug gap: set gap or replace spark plug as necessary; Verify ignition spark condition; Inspect spark plug cable, kill lead terminal at magneto and measure magneto air gap: replace terminals, set gap or replace magneto as necessary; Measure temperature of air intake and temperature rise across genset; remove blockage or prevent air recirculation; Dealers contact Distributor for technical support, Distributors contact factory for technical support |
| 15 | Underfrequency — Frequency less than 54Hz for 30 continuous seconds | Genset loads, Inverter/Charger, engine governor function, fuel supply, air fuel mixture, exhaust system, choke, demand regulator, carburetor, generator drive system, generator windings, ignition, wire connections | Verify that Last Fault is FC 15: Yes, continue diagnosis; No, troubleshoot actual last fault; Measure AC current while running genset with vehicle loads: identify faulty or short cycling loads; Determine battery charge rate (typical default is 80 percent): if adjustable reduce to 30 percent; Measure genset load capability with shop load bank (derate for altitude and temperature as necessary); Measure genset frequency and droop while running; Measure AC frequency while changing engine rpm to determine if frequency response matches engine rpm response: repair damaged generator drive system as necessary; Disconnect genset control P1 connector, verify P1 pins are fully inserted and inspect pin condition per PSB–676: insert, repair or replace pins as necessary; Reconnect P1 connector and test run genset for fault occurrence: repair or replace pins in connector as necessary; Check air filter cleanliness; replace air filter as necessary; Check for blocked or damaged exhaust system: repair or replace exhaust components as necessary; If the genset will not stay running measure genset frequency, quadrature winding and main winding voltages using Break-Out Tool 420–0603 and Instruction Sheet R1098; Gasoline Models: Vapor lock may occur in high ambient temperatures: operate in ambients at less than 120°F; verify proper installation to prevent air recirculation; correct as necessary; Verify steady DC voltage at fuel pump while genset is running; repair wiring as necessary; Run genset on shop fuel supply; verify tank level and fuel line condition in vehicle; Verify carburetor altitude setting; readjust as necessary; Verify choke operation, setting and linkage damage; readjust, repair or replace as necessary; Measure throttle stop frequency; readjust as necessary; Measure fuel pump pressure/flow: replace fuel filter or pump as necessary; Propane Models: When ambient temperatures are less than 40°F, vapor-withdrawal Propane tanks should be at least half full to provide proper vaporization rate; Propane having more than 2.5 percent Butane will not vaporize in ambients at less than 32°F; use HD–5 grade Propane; Verify steady DC voltage at fuel solenoid and priming solenoid (if so equipped) while genset is running; repair wiring as necessary; Verify clear vent hose; Run genset on shop fuel supply; verify tank level and fuel line condition in vehicle; Measure throttle stop frequency; readjust as necessary; Check genset fuel lines for damage: replace fuel line as required; Measure regulator lock off pressure; Verify priming solenoid operation, if so equipped; Check governor, actuator, linkage and spring for debris, damage and looseness: readjust and repair as necessary; Measure field, quadrature and main winding resistance: clean slip rings, replace brushes, repair harness and replace rotor or stator as necessary; Measure field, quadrature and main winding resistance to ground: clean slip rings, replace brushes, repair harness and replace rotor or stator as necessary; Measure field, quadrature and main winding resistance to each other: clean slip rings, replace brushes, repair harness and replace rotor or stator as necessary; Check brush alignment per PSB-682a; Verify that spark plug cable is secure on spark plug: reconnect or replace as necessary; Inspect ignition kill lead in harness and at connector P1: repair or replace lead, terminal or pins as necessary; Test magneto: Disconnect Connector P1; Connect positive(+) meter lead to chassis ground; Measure continuity to negative lead at pin P1–15: replace magneto as necessary; Measure spark plug gap: set gap or replace spark plug as necessary; Verify ignition spark condition; Inspect spark plug lead, kill lead terminal at magneto and measure magneto air gap: replace terminals, set gap or replace magneto as necessary; Measure temperature of air intake and temperature rise across genset; remove blockage or prevent air recirculation; Dealers contact Distributor for technical support, Distributors contact factory for technical support |
| 27 | Voltage Sense Lost — No Sense Voltage (0 VAC across S1–S2) for 1 continuous second after start disconnect | Genset loads, Inverter/Charger, VAC sense transformer, engine governor function, fuel supply, choke, demand regulator, carburetor, generator windings, ignition, wire connections, temperature | Verify that Last Fault is FC 27: Yes, continue diagnosis; No, troubleshoot actual last fault; Measure AC voltage; Determine battery charge rate (typical default is 80 percent): if adjustable reduce to 30 percent; Disconnect genset control P1 connector, verify P1 pins are fully inserted and inspect pin condition per PSB–676: insert, repair or replace pins as necessary; Reconnect P1 connector and test run genset for fault occurrence: repair or replace pins in connector as necessary; Check air filter cleanliness; replace air filter as necessary; Check for blocked or damaged exhaust system: repair or replace exhaust components as necessary; If the genset will not stay running measure genset frequency, quadrature winding and main winding voltages using Break-Out Tool 420–0603 and Instruction Sheet R1098; Gasoline Models: Under high ambient conditions or heat soak conditions vapor lock may occur, operate less than 120°F; verify proper installation to prevent air recirculation; correct as necessary; Verify steady DC voltage at fuel pump while genset is running; repair wiring, verify proper installation to prevent air recirculation as necessary; Run genset on shop fuel supply; verify tank level and fuel line condition in vehicle; Verify carburetor altitude setting; readjust as necessary; Verify choke operation, setting and linkage damage; readjust, repair or replace as necessary; Measure throttle stop frequency; readjust as necessary; Measure fuel pump pressure/flow: replace fuel filter or pump as necessary; Propane Models: When ambient temperatures are less than 40°F, vapor-withdrawal Propane tanks should be at least half full to provide proper vaporization rate; Propane having more than 2.5 percent Butane will not vaporize in ambients at less than 32°F; use HD–5 grade Propane; Verify steady DC voltage at fuel solenoid and priming solenoid (if so equipped) while genset is running; repair wiring as necessary; Verify clear vent hose; Run genset on shop fuel supply; verify tank level and fuel line condition in vehicle; Measure throttle stop frequency; readjust as necessary; Check genset fuel lines for damage: replace fuel line as required; Measure regulator lock off pressure; Verify priming solenoid operation, if so equipped; Check governor, actuator, linkage and spring for debris, damage and looseness: readjust and repair as necessary; Measure field, quadrature and main winding resistance: clean slip rings, replace brushes, repair harness and replace rotor or stator as necessary; Measure field, quadrature and main winding resistance to ground: clean slip rings, replace brushes, repair harness and replace rotor or stator as necessary; Measure field, quadrature and main winding resistance to each other: clean slip rings, replace brushes, repair harness and replace rotor or stator as necessary; Check brush alignment per PSB-682a; Verify that spark plug cable is secure on spark plug: reconnect or replace as necessary; Inspect ignition kill lead in harness and at connector P1: repair or replace lead, terminal or pins as necessary; Test magneto: Disconnect Connector P1; Connect positive(+) meter lead to chassis ground; Measure continuity to negative lead at pin P1–15: replace magneto as necessary; Measure spark plug gap: set gap or replace spark plug as necessary; Verify ignition spark condition; Inspect spark plug lead, kill lead terminal at magneto and measure magneto air gap: replace terminals, set gap or replace magneto as necessary; Measure temperature of air intake and temperature rise across genset; remove blockage or prevent air recirculation; Dealers contact Distributor for technical support, Distributors contact factory for technical support |
| 29 | High Battery Voltage — DC voltage to controller greater than 19 VDC when pressing start or stop | Incorrect battery configuration, wire damage, faulty charger, control | Verify that Last Fault is FC 29: Yes, continue diagnosis; No, troubleshoot actual last fault; Measure DC voltage at battery, genset and connector P1: reconnect battery or repair wiring as necessary; Measure DC voltage with battery charger on: reduce boost charge rate or diagnose faulty charger as necessary; If genset shares batteries with propulsion engine, check for fault using shop battery (voltage spike may cause fault): diagnose fault or voltage spikes from propulsion engine charging system; Disconnect genset control P1 connector, verify P1 pins are fully inserted and inspect pin condition per PSB–676: insert, repair or replace pins as necessary; Reconnect P1 connector and test run genset for fault occurrence: replace controller |
| 32 | Low Cranking Speed Sense — Prior to 2003 – quadrature frequency less than 1.7Hz for 2 continuous seconds after pressing start; After 2003 – quadrature frequency less than 1.7Hz for 12 continuous seconds after pressing start | Cylinder at TDC, fuel supply, air fuel mixture, exhaust system, starter, choke, demand regulator, carburetor, generator drive system, generator windings, ignition, wire connections | Verify that Last Fault is FC 32: Yes, continue diagnosis; No, troubleshoot actual last fault; Measure battery voltage at battery and genset: recharge or replace battery as necessary; Verify engine rotation manually: repair engine damage as necessary; Disconnect genset control P1 connector, verify P1 pins are fully inserted and inspect pin condition per PSB–676: insert, repair or replace pins as necessary; Reconnect P1 connector and test run genset for fault occurrence: repair or replace pins in connector as necessary; Measure DC voltage at starter during start attempt: repair wire connections, replace start solenoid and starter as necessary; Check air filter cleanliness; replace air filter as necessary; Check for blocked or damaged exhaust system: repair or replace exhaust components as necessary; Verify genset operation and outputs with Break-Out Tool 420–0603 and Instruction Sheet R1098; Measure AC frequency while changing engine rpm to determine if frequency response matches engine rpm response: repair damaged generator drive system as necessary; Gasoline Models: Vapor lock may occur in high ambient temperatures: operate in ambients at less than 120°F; verify proper installation to prevent air recirculation; correct as necessary; Measure steady DC voltage at fuel pump while genset is cranking: repair wiring as necessary; Try to start genset on shop fuel supply: verify tank level and fuel line condition in vehicle; Verify carburetor altitude setting; readjust as necessary; Verify choke operation, setting and linkage damage; readjust, repair or replace as necessary; Measure fuel pump pressure/flow: replace fuel filter or pump as necessary; Inspect carburetor butterfly for binding: replace carburetor as necessary; Propane Models: When ambient temperatures are less than 40°F, vapor-withdrawal Propane tanks should be at least half full to provide proper vaporization rate; Propane having more than 2.5 percent Butane will not vaporize in ambients at less than 32°F; use HD–5 grade Propane; Measure steady DC voltage at fuel solenoid and priming solenoid (if so equipped) while genset is running; repair wiring as necessary; Verify clear vent hose; Run genset on shop fuel supply; verify tank level and fuel line condition in vehicle; Check genset fuel lines for damage: replace fuel line as required; Measure regulator lock off pressure; Verify priming solenoid operation, if so equipped; Check governor, actuator, linkage and spring for debris, damage and looseness: readjust and repair as necessary; Verify that spark plug cable is secure on spark plug: reconnect or replace as necessary; Inspect ignition kill lead in harness and at connector P1: repair or replace lead, terminal or pins as necessary; Test magneto: Disconnect Connector P1; Connect positive(+) meter lead to chassis ground; Measure continuity to negative lead at pin P1–15 and P1–20: replace magneto as necessary; Measure spark plug gap: set gap or replace spark plug as necessary; Verify ignition spark condition; Inspect spark plug lead, kill lead terminal at magneto and measure magneto air gap: replace terminals, set gap or replace magneto as necessary; Measure temperature of air intake and temperature rise across genset; remove blockage or prevent air recirculation; Dealers contact Distributor for technical support, Distributors contact factory for technical support |
| 33 | Fault Code 33 — Single-Digit Fault to indicate shutdown due to Two-Digit Fault Code | Fault Code 3 interpreted as a non-assigned Fault Code 33 | Verify that Last Fault is FC 3: Yes, continue diagnosis; No, troubleshoot actual last fault; While LED is flashing three times press stop once (1 second duration): trouble shoot Two-Digit Fault Code |
| 35 | Control Card Failure — EEPROM (programming variables) error during self test | Faulty program | Verify that Last Fault is FC 35: Yes, continue diagnosis; No, troubleshoot actual last fault; Replace control |
| 36 | Genset Stopped Without Fault Condition — Quadrature frequency was less than 17 Hz (1020 rpm) when no other fault condition occurred | Auto Gen Start (AGS), fuel supply, air fuel mixture, exhaust system, loads, Inverter/Charger, choke, demand regulator, carburetor, generator drive system, generator windings, ignition, wire connections | Verify that Last Fault is FC 36: Yes, continue diagnosis; No, troubleshoot actual last fault; Verify whether AGS stopped genset: Yes, disable AGS or explain AGS function to customer (see PSB-666); No, continue diagnosis; Verify engine rotation manually: repair engine damage as necessary; Disconnect genset control P1 connector, verify P1 pins are fully inserted and inspect pin condition per PSB–676: insert, repair or replace pins as necessary; Reconnect P1 connector and test run genset for fault occurrence: repair or replace pins in connector as necessary; Check air filter cleanliness; replace air filter as necessary; Check for blocked or damaged exhaust system: repair or replace exhaust components as necessary; Measure AC current while running genset with vehicle loads: identify faulty or short cycling loads; Determine battery charge rate (typical default is 80 percent): if adjustable reduce to 30 percent; Measure genset load capability with shop load bank; Verify genset operation and outputs with Break-Out Tool 420–0603 and Instruction Sheet R1098; Measure AC frequency while changing engine rpm to determine if frequency response matches engine rpm response: repair damaged generator drive system as necessary; Gasoline Models: Vapor lock may occur in high ambient temperatures: operate in ambients at less than 120°F; verify proper installation to prevent air recirculation; correct as necessary; Verify steady DC voltage at fuel pump while genset is running; repair wiring as necessary; Run genset on shop fuel supply; verify tank level and fuel line condition in vehicle; Verify carburetor altitude setting; readjust as necessary; Verify choke operation, setting and linkage damage; readjust, repair or replace as necessary; Measure throttle stop frequency; readjust as necessary; Measure fuel pump pressure/flow: replace fuel filter or pump as necessary; Propane Models: When ambient temperatures are less than 40°F vapor-withdrawal Propane tanks should be at least half full to provide proper vaporization rate; Propane having more than 2.5 percent Butane will not vaporize in ambients at less than 32°F; use HD–5 grade Propane; Verify steady DC voltage at fuel solenoid and priming solenoid (if so equipped) while genset is running; repair wiring as necessary; Verify clear vent hose; Run genset on shop fuel supply; verify tank level and fuel line condition in vehicle; Measure throttle stop frequency; readjust as necessary; Check genset fuel lines for damage: replace fuel line as required; Measure regulator lock off pressure; Verify priming solenoid operation, if so equipped; Check governor, actuator, linkage and spring for debris, damage and looseness: readjust and repair as necessary; If the genset will not stay running measure genset frequency, quadrature winding and main winding voltages using Break-Out Tool 420–0603 and Instruction Sheet R1098; Remove connector P1 from control and re-install and try to start genset: inspect, repair or replace P1 connector pins as necessary; Measure field, quadrature and main winding resistance: clean slip rings, replace brushes, repair harness and replace rotor or stator as necessary; Measure field, quadrature and main winding resistance to ground: clean slip rings, replace brushes, repair harness and replace rotor or stator as necessary; Measure field, quadrature and main winding resistance to each other: clean slip rings, replace brushes, repair harness and replace rotor or stator as necessary; Check brush alignment per PSB-682a; Measure temperature of air intake and temperature rise across genset; remove blockage or prevent air recirculation; Dealers contact Distributor for technical support, Distributors contact factory for technical support |
| 42 | Processor Fault — ROM (programming variables) error during self test | Faulty program | Verify that Last Fault is FC 42: Yes, continue diagnosis; No, troubleshoot actual last fault; Replace control |
| 43 | Processor Fault — RAM (programming variables) error during self test | Faulty program | Verify that Last Fault is FC 43: Yes, continue diagnosis; No, troubleshoot actual last fault; Replace control |
| 48 | Field Sense Fault — Controller unable to sense field voltage | Faulty control | Verify that Last Fault is FC 48: Yes, continue diagnosis; No, troubleshoot actual last fault; Replace control |
| 51 | Processor Failure — Processor error | Faulty control | Verify that Last Fault is FC 51: Yes, continue diagnosis; No, troubleshoot actual last fault; Replace control |
| Symptom | Cause | Remedy |
|---|---|---|
| Status indicator light dead | Faulty connections, no battery voltage | Try the genset Start Switch if the remote Start Switch does not work, and vice versa; Clean and tighten the positive (+) and negative (−) battery cable connections at the battery, vehicle frame and genset; Recharge or replace the battery. Refer to the battery manufacturer's recommendations. |
| Starting batteries run down | Marginal batteries, connections, or charging system or, parasitic loads | Clean and tighten the positive (+) and negative (−) battery cable connections at the battery, vehicle frame and genset; Recharge or replace the battery. Refer to the battery manufacturer's recommendations; Have a battery charging system installed or serviced in the vehicle. |
| Starter engages-disengages | Cranking voltage dips below 6 volts—low battery charge, poor connections, long cables | Have the vehicle propulsion engine running while trying to start the genset—the battery charging alternator may be able to maintain starting voltage high enough to get the genset started; Clean and tighten the positive (+) and negative (−) battery cable connections at the battery, vehicle frame and genset; Recharge or replace the battery. Refer to the battery manufacturer's recommendations; Increase battery cable size or run parallel cables. |
| Status indicator light goes out while cranking—no start | Internal short circuit caused automatic-reset circuit protective device to trip | Try starting again. See an authorized Onan dealer if the status indicator light flashes and then goes out again without the engine starting. |
| No power—genset running, status light on | Line circuit breaker OFF, or tripped due to short circuit or overload | Turn on or reset the line circuit breaker on the genset (Page 2-3); Turn on or reset the line circuit breakers on the main distribution panel in the vehicle. |
| Genset starts or stops without command – no fault code | Low battery voltage; shorted harness connection; faulty start/stop switch; Auto Gen Start (AGS) is enabled | Check last fault and record; Measure battery voltage at battery and genset; Inspect battery connections and cables for cleanliness, tightness and damage: clean, tighten and repair connections and cables as necessary; Check electrolyte level and hydrometer reading in maintenance type batteries: replace electrolyte and recharge or replace battery as necessary; Disconnect genset control P1 connector, verify P1 pins are fully inserted and inspect pin condition per PSB–676: insert, repair or replace pins as necessary; Reconnect P1 connector and test run genset for symptom: repair or replace pins in connector as necessary; Measure battery voltage at genset while attempting to start from local or remote switch: recharge or replace battery if voltage drops below 9 VDC, test and service genset battery charger if so equipped, increase battery cable size or run parallel cables; Measure battery voltage and check for charger increase while genset is running; Measure for continuity change across start/stop switch between neutral and start position and neutral and stop position at switches and at connector P1: reconnect or repair connections, replace switches as necessary; Measure for continuity from start and stop inputs to ground at switches and at connector P1: Repair or replace damaged harness; Determine if AGS is installed and enabled (AGS will command start and stop based on its own settings): disable AGS or explain AGS function to customer (see PSB-666) |
| No response – status indicator light dead | Low/No battery voltage; poor battery connection; faulty battery; open harness connection; faulty start/stop switch; faulty LED | Measure battery voltage at battery, at genset and at connector P1: reconnect, clean, repair and replace connections as necessary; Measure battery voltage at genset while attempting to start or prime from local or remote switch: recharge or replace battery if voltage drops below 9 VDC, test and service genset battery charger if so equipped, increase battery cable size or run parallel cables; Measure for continuity change across start/stop switch between neutral and start position and neutral and stop position at switches and at connector P1: reconnect or repair connections, replace switches as necessary; Test switches LED by energizing with 12 VDC: replace switches as necessary; Disconnect genset control P1 connector, verify P1 pins are fully inserted and inspect pin condition per PSB–676: insert, repair or replace pins as necessary; Reconnect P1 connector and test run genset for start and prime operation: replace control as necessary |
| Starting batteries run down | Battery connections; battery; charging system; excessive cranking; excessive priming | Measure battery voltage at battery and genset; Inspect battery connections and cables for cleanliness, tightness and damage: clean, tighten and repair connections and cables as necessary; Check electrolyte level and hydrometer reading in maintenance type batteries: replace electrolyte and recharge or replace battery as necessary; Verify battery charger is on and check operation; Measure battery voltage and check for charging increase while genset is running; Check last fault and record: troubleshoot as necessary; Disconnect genset control P1 connector, verify P1 pins are fully inserted and inspect pin condition per PSB–676: insert, repair or replace pins as necessary; Reconnect P1 connector and test run genset for fault occurrence: repair or replace pins in connector as necessary; Measure for continuity change across start/stop switch between neutral and stop position at switches and P1 connector: replace switches as necessary or disconnect external stop device if so equipped; Measure for voltage at fuel pump while genset is not running or being primed: replace control as necessary |
| Starter engages – disengages | Battery connections; battery; charging system; start/stop switches; engine compression | Measure battery voltage at battery and genset; Inspect battery connections and cables for cleanliness, tightness and damage: clean, tighten and repair connections and cables as necessary; Check electrolyte level and hydrometer reading in maintenance type batteries: replace electrolyte and recharge or replace battery as necessary; Disconnect genset control P1 connector, verify P1 pins are fully inserted and inspect pin condition per PSB–676: insert, repair or replace pins as necessary; Reconnect P1 connector and test run genset for fault occurrence: repair or replace pins in connector as necessary; Measure battery voltage at genset while attempting to start from local or remote switch: recharge or replace battery if voltage drops below 9 VDC, test and service genset battery charger if so equipped, increase battery cable size or run parallel cables; Measure battery voltage and check for charger increase while genset is running |
| No AC power – genset running, status LED on steady | Circuit breakers | Measure AC output at genset circuit breaker: reset or turn on genset circuit breaker, diagnose faulty loads as necessary |
| Genset cranks but does not start – no fault code | Not holding start switch long enough to cause fault | Check and record last fault code; Crank genset and hold switch until control stops cranking and displays fault code (approximately 30 seconds): troubleshoot fault code and reference last fault code recorded above if necessary |
| Genset runs but stops when switch is released – no fault code | Not holding start switch long enough to cause fault | Check and record last fault code; Start genset and hold switch until control shuts down and displays fault code (approximately 30 seconds): troubleshoot fault code and reference last fault code recorded above if necessary |
Fault codes and symptom→remedy steps extracted from this model’s service/owner documentation; verify against the official manual before servicing.
Documented causes: Marginal batteries, connections, or charging system or, parasitic loads; Battery connections; battery; charging system; excessive cranking; excessive priming. See the table for the matching fixes.
Documented causes: Faulty connections, no battery voltage. See the table for the matching fixes.
Documented causes: Cranking voltage dips below 6 volts—low battery charge, poor connections, long cables. See the table for the matching fixes.