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Every Kohler engine fault code in our verified reference — 24 codes, 18 of them with a documented remedy. Find your code in the table, read the likely causes, then work the remedy. If it is beyond a field fix, our workshop in Embakasi repairs Kohler controllers and engines at board level.
Covers: 14RES/RESL and 20RES/RESL · C13/C15/C18
| Code | Fault | Likely cause | Remedy |
|---|---|---|---|
| 91-2 | Accelerator Pedal Position 1: Erratic | Intermittent; indicating a failure or overload. | — |
| 91-3 | Accelerator Pedal Position 1: Voltage Above Normal | triggering a shutdown. | Check for shorts to power. Inspect sensor. Replace if necessary. |
| 91-4 | Accelerator Pedal Position 1: Voltage Below Normal | Locate and release the emergency stop button on the APM303 panel by twisting or pulling as per design. Check for safety conditions that triggered the activation. Inspect the button’s wiring for faults. Reset the fault on the control panel and attempt to restart. If the fault persists; consult the SDMO APM303 or a technician. | Check for open circuits. Inspect sensor. Replace if necessary. |
| 91-8 | Accelerator Pedal Position 1: Abnormal Frequency | Pulse Width; shorts; opens). Replace the sensor if faulty. Prime the fuel system if needed. Reset the fault and restart. to the APM303 or a technician if unresolved. | Check the fuel level in the daily tank; refill with clean diesel fuel. Inspect for fuel leaks in the tank or lines. Test the fuel level sensor and wiring for faults (e.g. |
| 97-3 | Water In Fuel Indicator: Voltage Above Normal | worn pump). Reset the fault and restart. Consult the APM303 or a technician if unresolved. | Check wiring for shorts to power. Inspect switch. Replace if necessary.; Check the engine oil level; top up with the recommended oil if low. Inspect for oil leaks. Test the oil pressure sensor and wiring for faults; replace if defective. Perform an oil pressure test to check for internal engine issues (e.g. |
| 100-3 | Engine Oil Pressure: Voltage Above Normal | — | Check sensor wiring for shorts. Inspect oil pressure sensor. Replace if faulty.; Check the coolant level; top up if low. Inspect the cooling system for leaks or blockages. Ensure the radiator is clean and vents are clear. Test the coolant temperature sensor and wiring; replace if faulty. Verify thermostat operation. Reset the fault and restart. Consult the APM303 or a technician if unresolved. |
| 100-4 | Engine Oil Pressure: Voltage Below Normal | 1500 RPM for 50 Hz). Inspect the governor or throttle for miscalibration or faults. Check the fuel system for over-fueling issues. Test the speed sensor and wiring | Check for open circuits. Inspect sensor. Replace if necessary.; Verify the engine speed is within nominal limits (e.g.; replace if faulty. Reset the fault and restart. to the APM303 or a technician if unresolved. |
| 486-3 | Engine Fan Reverse Switch: Voltage Above Normal | causing a shutdown. | Check wiring and connections for shorts to power. Inspect fan reverse switch. Replace if faulty. |
| 486-4 | Engine Fan Reverse Switch: Voltage Below Normal | preventing optimal engine starting conditions. | Check for open circuits or poor connections. Inspect fan reverse switch. Replace if faulty. |
| 544-2 | Engine Cooling Fan Speed Sensor: Erratic | Intermittent; preventing engine start and triggering a shutdown. | — |
| 544-8 | Engine Cooling Fan Speed Sensor: Abnormal Frequency | Pulse Width; indicating a potential fault. | — |
| 774-2 | Accelerator Pedal Position 2: Erratic | Intermittent; opens; or loose terminals. Test the relay for proper operation | Inspect the differential relay wiring and connections for shorts; replace if faulty. Verify the relay settings match the generator specifications. Reset the fault and test operation. to the SDMO or a technician if unresolved. |
| 774-3 | Accelerator Pedal Position 2: Voltage Above Normal | opens; or loose terminals. Test the monitor for proper operation | Check for shorts to power. Inspect sensor. Replace if necessary.; Check the insulation monitor wiring and connections for shorts; replace if faulty. Verify the monitor settings are correct. Reset the fault and test operation. Consult the SDMO or a technician if unresolved. |
| 774-4 | Accelerator Pedal Position 2: Voltage Below Normal | indicating a warning. | Check for open circuits. Inspect sensor. Replace if necessary. |
| 774-8 | Accelerator Pedal Position 2: Abnormal Frequency | Pulse Width; preventing charging and triggering a shutdown. | — |
| 1076-5 | Engine Cooling Fan Bypass Solenoid: Current Below Normal | triggering a shutdown. | Check solenoid wiring for open circuits. Test solenoid. Replace if necessary. |
| 1076-6 | Engine Cooling Fan Bypass Solenoid: Current Above Normal | — | Check for shorts to ground. Inspect solenoid. Replace if faulty.; Inspect the generator’s electrical output cables and connections for insulation breakdown or damage. Test the insulation resistance using a megger. Check the insulation monitor wiring and settings. Reset the alarm and test operation. to the SDMO or a technician if the alarm persists. |
| 1937-2 | Engine Coolant Flow Switch: Erratic | Intermittent; triggering a shutdown. | — |
| LCb | Low cranking voltage | Charge or replace the battery.; opens; or loose connections. Verify the module is correctly installed and powered. Reset the control panel and test communication. If unresolved | Check the CAN bus wiring and connectors for the option 6 module for shorts; replace the module or to the SDMO or a technician. |
| Lead 13 and Ground (Low Oil Pressure - LOP Switch) | Checks continuity of the low oil pressure switch | indicating oil pressure status.; ensure it is not stuck open. Inspect contactor wiring and control signals for faults. Verify ATS configuration. Reset the alarm and test operation. Consult the SDMO or a technician if the issue persists. | Check the emergency power contactor (generator side) for proper operation |
| LOP | Low oil pressure | opens; or loose connections. Verify the spare module is powered and correctly configured. Reset the control panel and test communication. If the fault persists; consult the SDMO or a technician. | Check the engine oil level regularly as recommended in the O/M. Check for leaks in the lubrication system. Check the oil level and add oil if the level is low. Check low oil pressure switch connections and operation. Check the oil pump and lubrication system. O/M 5.10 Engine S/M.; Inspect the RS485 communication cables and connectors for shorts |
| Lr | Locked rotor | 5.4.; Power cycle the generator by disconnecting the battery for 30 seconds and reconnecting. Check for software updates for the control panel. Inspect control panel wiring for faults. If the fault persists; the control module may need replacement. Consult the SDMO or a technician. | Check mag pickup connections and operation. Check for a locked rotor. 5.9.4 |
| P1-9 and P1-10 (Temperature Sensor - CTS) | Checks the resistance of the coolant temperature sensor | indicating engine temperature. | Verify the normal power contactor (system side) is functioning and not stuck open. Inspect contactor wiring and control signals for faults. Check the automatic transfer switch (ATS) settings. Reset the alarm and test operation. to the SDMO or contact a technician if unresolved. |
| QCON1 and QCON2 (Magnetic Pickup) | Checks resistance of the magnetic pickup | used for engine speed sensing.; triggering a shutdown. | — |
Codes and descriptions are industry-standard identifiers reproduced for identification only. This reference is not affiliated with or endorsed by Kohler; for official procedures always refer to the manufacturer’s service manual for your specific engine. A dash means our registry holds no verified entry for that column — we publish the gap rather than fill it in.
Send us the code and the engine serial. We diagnose Kohler sets on site across all 47 counties, and repair controllers at board level on the bench in Embakasi.