Cummins/Onan LSG-423 troubleshooting: 7 fault codes and 16 symptom-cause-remedy entries from the manufacturer's own service documentation.
Cummins/Onan LSG-423 — full specs, parts & maintenance.
All Cummins/Onan fault codes →
| Code | Meaning | Remedy |
|---|---|---|
| 32 | High Coolant Temperature | |
| 32A | Emergency Stop | Reset the emergency stop switch. |
| 40 | Pre High Coolant Temp. | |
| 41 | Pre Low Oil Pressure | Check and adjust oil level or replace oil pump. |
| 62 | Low Battery Volts | |
| 63 | Low Fuel | Refuel the generator set. |
| 48 | Emergency Stop |
| Symptom | Cause | Remedy |
|---|---|---|
| Green RUN lamp lights following engine startup | Indicates all engine systems are normal. No corrective action required. | |
| PRE HET/LOP lamp lights. Engine continues to operate | Engine has begun to overheat and engine temperature has risen to approximately 205°F (97° C) or coolant level is low | If generator is powering non-critical and critical loads and cannot be shut down, use the following: Reduce load if possible by turning off non-critical loads; Check air inlets and outlets and remove any obstructions to airflow |
| HI ENG TEMP lamp lights. Engine shuts down | Engine has overheated (engine temperature has risen above 215°F/102°C) or coolant level is low | Allow engine to cool down completely before proceeding with the following checks: Check coolant level and replenish if low. Look for possible coolant leakage points and repair if necessary; Check for obstructions to cooling airflow and correct as necessary; Check for a slipping fan belt and tighten if loose; Reset control and restart after locating and correcting problem. Contact an authorized service center if none of the above |
| LO OIL PRES lamp lights. Engine shuts down | Engine oil pressure has dropped to 25 psi (172 kPa) | Check oil level, lines and filters. If oil system is OK but oil level is low, replenish. Reset control and restart. Contact an authorized service center if oil pressure is not in the range of 40 to 65 psi (275 to 448 kPa) |
| OVERCRANK lamp lights and engine stops cranking. or Engine runs, shuts down, and LO OIL PRES lamp lights | Possible fuel system problem | Check for empty fuel tank (LPG Vapor), fuel leaks, or plugged fuel lines and correct as required; Check for dirty fuel filter and replace if necessary (see Maintenance section); Check for dirty or plugged air filter and replace if necessary (see Maintenance section); Reset the control and restart after correcting the problem. Contact an authorized service center for service if none of the above |
| Engine runs and then shuts down, OVERSPEED lamp lights | Engine has exceeded normal operating speed | Contact an authorized service center for service |
| SWITCH OFF lamp flashes | Run/Stop/Remote switch is in the Stop position which will prevent automatic starting if an automatic transfer switch is used | Move the Run/Stop/Remote switch to the Remote position for automatic starting |
| LO FUEL lamp lights. Engine continues to run....or LO FUEL lamp lights. Engine shuts down and LO OIL PRES lamp lights | Interruption of natural gas supply | Install the fuel hose and regulator supplied with the unit and connect to a propane fuel supply. Move the selector switch below control panel to the PROPANE position |
| The OVERLOAD lamp lights. Engine shuts down | The line circuit breaker is located in the ATS or generator set output box. If load exceeds generator current rating, the breaker will trip preventing the generator from being overloaded | Locate the source of overload and correct as necessary. Manually reset breaker to reconnect the load to the generator |
| Fault lamp lights but no fault exists. Engine gauges show oil pressure, engine temperature, and frequency (speed) are within normal limits | The monitor board or a sensor may be at fault | Contact an authorized service center for service |
| Engine will not crank | Possible fault with control or starting system: Fault lamp on | Correct fault and reset control |
| Engine will not crank | Possible fault with control or starting system: Poor battery cable connections | Clean the battery cable terminals and tighten all connections |
| Engine will not crank | Possible fault with control or starting system: Discharged or defective battery | Recharge or replace the battery |
| Engine will not crank | Possible fault with control or starting system: Emergency stop button pushed in | To reset, pull switch out and move Run/Stop/Remote switch to Stop position. Then push test switch to Reset/Lamp position |
| Engine will not crank | Possible fault with control or starting system | Contact an authorized service center if none of the above |
| No AC output voltage | Field breaker is tripped | Reset breaker. Contact an authorized service center if voltage buildup causes breaker to trip |
Fault codes and symptom→remedy steps extracted from this model’s service/owner documentation; verify against the official manual before servicing.
Documented causes: Possible fault with control or starting system: Fault lamp on; Possible fault with control or starting system: Poor battery cable connections; Possible fault with control or starting system: Discharged or defective battery; Possible fault with control or starting system: Emergency stop button pushed in. See the table for the matching fixes.
Documented causes: Engine has begun to overheat and engine temperature has risen to approximately 205°F (97° C) or coolant level is low. See the table for the matching fixes.
Documented causes: Engine has overheated (engine temperature has risen above 215°F/102°C) or coolant level is low. See the table for the matching fixes.