Kohler 18TRES troubleshooting: 25 fault codes and symptom-cause-remedy entries from the manufacturer's own service documentation.
Kohler 18TRES — full specs, parts & maintenance.
| Code | Meaning | Cause | Remedy |
|---|---|---|---|
| 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. | |
| AF | Auxiliary fault input shutdown | Indicates a shutdown initiated by pushing the emergency stop switch. (TRES models only) | Check the position of the emergency stop button. (TRES models only) |
| Symptom | Cause | Remedy |
|---|---|---|
| Line circuit breaker trips or fuses blow repeatedly | See Section 4, Troubleshooting, for possible causes | |
| Controller LED display is off | No power to the controller: Controller fuse (F3) is blown. | Replace the fuse. If the fuse blows again, contact an authorized distributor/dealer. Low or no battery voltage. Check connections. Check the engine starting battery and battery charger. See Figure 4-3. |
| The generator set does not crank. | Fault shutdown | Check for a fault code on the controller display. See Section 2.6. Battery weak or dead Check power to the battery charger. Recharge or replace the battery. Battery charger fuse blown Replace the fuse. Contact an authorized distributor/dealer for service if fuse blows repeatedly. |
| The generator set cranks but does not start, starts hard, lacks power, or operates erratically. | Air cleaner clogged | Clean and/or replace the air cleaner. Battery weak or dead Check power to the battery charger. Recharge or replace the battery. Battery connection poor Clean and tighten the battery connections. Spark plug wire connection loose Check the spark plug wires. Low oil pressure shutdown Check the oil level. Fuel pressure insufficient Check the fuel supply and valves. Engine malfunction Contact an authorized distributor/dealer. |
| No AC output. | AC circuit breaker in the OFF position | Place the circuit breaker in the ON position. AC circuit breaker tripping because of overload Reduce the load on the generator set. AC circuit breaker tripping because of short circuit Contact an authorized distributor/dealer for service. |
| Generator set stops suddenly. | Low oil pressure shutdown | Check the oil level. Check for signs of oil leaks. Out of fuel Check fuel supply. Overcrank shutdown Reset the controller. If the overcrank fault occurs again, contact an authorized distributor/dealer. |
| Generator set master switch in the OFF/RESET position | Move the switch to the correct position (RUN or AUTO). | |
| Remote stop command received from a remote switch or ATS | Check the remote switch position. | |
| Engine malfunction | Contact an authorized distributor/dealer. | |
| Auxiliary winding fuse (F1) blown | Replace the fuse. Contact an authorized distributor/dealer for service if fuse blows repeatedly. | |
| Low output or excessive drop in voltage. | Generator set overloaded Reduce the load. | |
| Controller fuse (F3) blown | Replace the fuse. If the fuse blows again, contact an authorized distributor/dealer. |
Fault codes and symptom→remedy steps extracted from this model’s service/owner documentation; verify against the official manual before servicing.
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.
Documented causes: 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.. See the table for the matching fixes.