Kohler 18RES troubleshooting: 22 fault codes and symptom-cause-remedy entries from the manufacturer's own service documentation.
Kohler 18RES — full specs, parts & maintenance.
| Code | Meaning | Cause | Remedy |
|---|---|---|---|
| High engine temperature | Engine runtime, hours | ||
| Low battery voltage | Crank cycle status | ||
| Overcrank | Remote two-wire start/stop capability | ||
| Overfrequency | Digital voltage regulation: ±1.5% RMS no-load to full-load | ||
| Overspeed | Automatic start for programmed cranking cycle | ||
| Underfrequency | Master control switch mounted on the junction box: Run/Off-Reset/Auto | ||
| Undervoltage | Upgradeable application software | ||
| AF | Indicates a shutdown initiated by pushing the emergency stop switch. | Not used on RES models. | Check the position of the emergency stop button. (TRES models only) |
| HE | High engine temperature shutdown | Shutdown occurs if the engine coolant temperature exceeds the maximum temperature for more than 5 seconds. This function becomes active after the engine reaches the crank disconnect speed. | Check for blocked air inlets and exhaust outlets. |
| LOP | Low oil pressure shutdown | Shutdown occurs if a low oil pressure condition exists for more than 5 seconds. This function becomes active 30 seconds after the engine has reached crank disconnect speed (30 second inhibit). Note: The low oil pressure shutdown does not protect against low oil level. Check the oil level at the engine. | Check for leaks in the lubrication system. Check the oil level and add oil if the level is low. |
| OC | Overcrank shutdown | Shutdown occurs after 3 unsuccessful starting attempts. The crank cycle is set for three starting attempts of 15 seconds cranking and 15 seconds rest. | Check the fuel supply, spark plug, and battery. Check for loose connections. Contact an authorized distributor/dealer for service if problem continues. |
| Locked rotor | The generator set also shuts down on OC if no engine rotation is sensed during cranking. Shuts down 3 seconds after the fault is detected. | ||
| OF | Overfrequency shutdown | Shutdown occurs when the governed frequency exceeds 110% of the system’s frequency setpoint for more than 5 seconds. This function becomes active 10 seconds after engine start (10 second inhibit). | Contact an authorized distributor/dealer for service if problem continues. |
| OS | Overspeed shutdown | Shutdown occurs if the engine speed exceeds 110% of the normal running speed for more than 0.3 seconds. | Contact an authorized distributor/dealer for service if problem continues. |
| OU | Overvoltage shutdown | Shutdown occurs if the voltage exceeds 120% of the system nominal voltage for more than 2 seconds. | Contact an authorized distributor/dealer for service if problem continues. |
| UF | Underfrequency shutdown | Shutdown occurs if the governed frequency falls below 54 Hz for more than 5 seconds. Shutdown also occurs if the governed frequency falls below 56.5 Hz for more than 60 seconds. This function becomes active 10 seconds after engine start. (10 second inhibit). | Reduce the load and restart the generator set. Contact an authorized distributor/dealer for service if problem continues. |
| UU | Undervoltage shutdown | Shutdown occurs if the voltage falls below 80% of the nominal system voltage for more than 10 seconds. | Reduce the load and restart the generator set. Contact an authorized distributor/dealer for service if problem continues. |
| HB | High battery voltage warning | Fault code is displayed if the engine starting battery voltage rises above 16 VDC for more than 30 seconds when the engine is running. Not operative during the engine crank cycle, this fault condition does not inhibit engine starting. | Check the battery rating and condition. Check the battery charger operation. |
| LB | Low battery voltage warning | Fault code is displayed if the engine starting battery voltage falls below 11 VDC for more than 30 seconds when the engine is not running. Not operative during the engine crank cycle, this fault condition does not inhibit engine starting. |
| Symptom | Cause | Remedy |
|---|---|---|
| Severe electrical equipment damage. | Welding the generator set. | Never weld components of the generator set without first disconnecting the battery, controller wiring harness, and engine electronic control module (ECM). |
| Accidental starting | Disconnect the battery cables before working on the generator set. Remove the negative (--) lead first when disconnecting the battery. Reconnect the negative (--) lead last when reconnecting the battery. | |
| Battery short circuit | Disconnect the battery before generator set installation or maintenance. Remove all jewelry before servicing the equipment. Use tools with insulated handles. Remove the negative (--) lead first when disconnecting the battery. Reconnect the negative (--) lead last when reconnecting the battery. Never connect the negative (--) battery cable to the positive (+) connection terminal of the starter solenoid. Do not test the battery condition by shorting the terminals together. |
Fault codes and symptom→remedy steps extracted from this model’s service/owner documentation; verify against the official manual before servicing.
Documented causes: Welding the generator set.. See the table for the matching fixes.
Documented causes: Not used on RES models.. See the table for the matching fixes.
Documented causes: Shutdown occurs if the engine coolant temperature exceeds the maximum temperature for more than 5 seconds. This function becomes active after the engine reaches the crank disconnect speed.. See the table for the matching fixes.