Generac NP-30G troubleshooting: 11 fault codes and 142 symptom-cause-remedy entries from the manufacturer's own service documentation.
Generac NP-30G — full specs, parts & maintenance.
| Code | Meaning | Remedy |
|---|---|---|
| QA | W WARNING | |
| M01 | Low Oil Pressure Shutdown | Check the engine oil level. If necessary, add oil to the FULL mark. |
| M02 | High Temperature Shutdown | |
| M03 | Overspeed Shutdown | Do not attempt a manual adjustment to control engine speed. |
| M04 | Low Voltage Shutdown | |
| C1 | Low Oil Pressure Shutdown | Check the engine oil level. |
| T1 | High Temperature Shutdown | |
| S1 | Overspeed Shutdown | Do not attempt a manual adjustment to control the engine speed. |
| V1 | Low Voltage Shutdown | |
| C2 | High Temperature Shutdown | |
| C4 | Low Voltage Shutdown | Disconnect all loads the generator might power by whatever means provided, such as the recreational vehicle’s main circuit breaker. |
| Symptom | Cause | Remedy |
|---|---|---|
| Engine won't crank | 15 amp fuse is blown | Replace 15 amp fuse |
| Engine won't crank | Loose corroded or defective battery cables | Tighten, clean or replace as necessary |
| Engine won't crank | Defective engine Start/Stop switch | Replace Start/Stop switch |
| Engine won't crank | Defective starter contactor | Replace contactor |
| Engine won't crank | Defective starter motor | Replace starter motor |
| Engine won't crank | Low or defective battery | Change or replace battery |
| Engine cranks but won't start | Out of fuel | Replenish fuel |
| Engine cranks but won't start | Fuel pump is defective | Replace fuel pump |
| Engine cranks but won't start | Open Wire #14 from Eng. Control Bd. | Reconnect wire |
| Engine cranks but won't start | Engine is flooded | Wait 5-10 min. before trying |
| Engine cranks but won't start | Spark plug defective | Clean, regap or replace plug |
| Engine starts hard, runs rough, low full load power | Air cleaner plugged or damaged | Clean or replace as needed |
| Engine starts hard, runs rough, low full load power | Defective spark plug | Clean, regap or replace plug |
| Engine starts hard, runs rough, low full load power | Loose spark plug boot | Press boot on securely |
| Engine starts, shuts down when Start/Stop switch is released | Engine oil is low | Check oil; add as needed |
| Engine starts, shuts down when Start/Stop switch is released | Engine is overheated | Check for adequate ventilation |
| Engine starts, shuts down when Start/Stop switch is released | Defective Low Oil Pressure System | Have serviced/replaced |
| Engine starts, shuts down when Start/Stop switch is released | Defective Engine Control Board | Have board serviced/replaced |
| Engine starts, shuts down when Start/Stop switch is released | Defective Computer Control Board | Have board serviced/replaced |
| Start/Stop switch at Stop, engine continues to run | Defective Start/Stop switch | Replace switch |
| Start/Stop switch at Stop, engine continues to run | Open/disconn | |
| No AC voltage can be measured across Stator connections at the Battery Charge Rectifier (BCR) | An open circuit condition probably exists in Wire 66 (Brown), or Wire 77 (Brown) | |
| AC voltage is available to the Wire 66 and 77 terminals at the Battery Charge Rectifier, but no voltage or a low voltage is measured between the BCR's Wire 55 terminal and ground | The Battery Charge Rectifier (BCR) is defective | |
| No AC voltage is measured at the Wires 66 and 77 terminals of the Battery Charge Rectifier, with the unit running | An open circuit exists in the wire 66 or 77 circuit | |
| AC voltage was present at the Wires 66 and 77 terminals of the Battery Charge Rectifier, but DC voltage is NOT present between the Battery Charge Rectifier's Wire 55 and frame ground | The Battery Charge Rectifier (BCR) is defective | |
| The engine starts, but the Stepper Motor does not move, and engine shuts down after several seconds | The CCG circuit board's micro-controller may not be operating | |
| Engine starts, but Stepper Motor does not move. The engine accelerates uncontrollably and shuts down when engine speed exceeds 4500 rpm | A failure of the circuit board's Stepper Motor drive | |
| Engine starts, but Stepper Motor does not move. Engine appears to operate too slowly; Engine is not able to handle the load and unit operates at low AC output voltage; After several seconds under load, AC output voltage is turned off (overload condition) | A failure of the circuit board's Stepper Motor drive | |
| The engine can be started, but shuts down after several seconds | A timing detection failure may have occured (Timing winding, Wires TIM1, TIM2) | |
| The engine speed and output voltage are erratic under constant load, but the AC output does not turn off intermittently | Erratic timing detection may have occured (Timing winding, Wires TIM1, TIM2) | |
| Premature high temperature shutdowns | Some early production units were equipped with a 265° F. switch | The 265° F. switch should be removed and replaced with the Part No. 94090 switch |
| Engine starts, accelerates, shuts down at 4500 rpm | Carburetor linkage sticking with throttle stuck open | Repair sticking throttle |
| Engine starts, accelerates, shuts down at 4500 rpm | Stepper Motor failed or seized | Replace Stepper Motor |
| Engine starts, accelerates, shuts down at 4500 rpm | Stepper Motor wire connections broken or disconnected | Reconnect or repair |
| Engine starts, accelerates, shuts down at 4500 rpm | Stepper Motor not properly connected | Reconnect wires |
| Overvoltage condition and speed control system cannot reduce output voltage | Carburetor linkage sticking with throttle stuck partly open | Repair sticking throttle |
| Overvoltage condition and speed control system cannot reduce output voltage | Stepper Motor failed or seized | Replace Stepper Motor |
| Overvoltage condition and speed control system cannot reduce output voltage | Connection to Stepper Motor is broken/disconnected with throttle open | Repair or replace connections |
| Overvoltage condition and speed control system cannot reduce output voltage | Stepper Motor not properly connected | Reconnect Stepper Motor wires |
| Engine speed is maintained and no-load voltage is good. However, when load is applied output voltage drops and engine shuts down | Carburetor linkage sticking with throttle partly open | Repair sticking throttle |
| Engine speed is maintained and no-load voltage is good. However, when load is applied output voltage drops and engine shuts down | Stepper Motor failed or seized | Replace Stepper Motor |
| Engine speed is maintained and no-load voltage is good. However, when load is applied output voltage drops and engine shuts down | Connection to Stepper Motor broken or disconnected | Repair or replace connections |
| Engine speed is maintained and no-load voltage is good. However, when load is applied output voltage drops and engine shuts down | Stepper Motor not properly connected | Reconnect Stepper Motor |
| Engine does not accelerate when load is applied. After 10 seconds, engine shuts down | Carburetor linkage sticking with throttle stuck closed | Repair sticking throttle |
| Engine does not accelerate when load is applied. After 10 seconds, engine shuts down | Stepper Motor failed or seized | Replace Stepper Motor |
| Engine does not accelerate when load is applied. After 10 seconds, engine shuts down | Stepper Motor not properly connected | Reconnect Stepper Motor |
| Engine speed and AC output voltage erratic under constant load. AC output does not turn off intermittently | Stepper Motor failure | Replace Stepper Motor |
| Engine speed and AC output voltage erratic under constant load. AC output does not turn off intermittently | Connection to Stepper Motor broken or disconnected | Repair or replace connections |
| Engine speed and AC output voltage erratic under constant load. AC output does not turn off intermittently | Stepper Motor not properly connected | Reconnect Stepper Motor |
| Engine speed and AC output voltage erratic under constant load. AC output does not turn off intermittently | CCG board failure (erratic detection of "zero voltage" crossings) | Replace CCG Circuit Board |
| Engine starts but Stepper Motor does not move. Shut down occurs after several seconds | Power Supply winding (PS1, PS2) is open | Repair or replace bad wire(s) PS1/PS2 or replace Stator |
| Engine starts but Stepper Motor does not move. Shut down occurs after several seconds | Stator Timing winding is open | Repair/replace bad wire(s) TIM1/TIM2 or replace Stator |
| Engine starts but Stepper Motor does not move. Shut down occurs after several seconds | Power supply winding in Stator shorted to ground | Replace Stator |
| Engine starts but Stepper Motor does not move. Shut down occurs after several seconds | Timing winding in Stator shorted to ground | Replace Stator |
| Engine starts but Stepper Motor does not move. Shut down occurs after several seconds | CCG board does not detect "Zero Voltage" crossings | Replace CCG circuit board |
| Engine shuts down but overspeed above 4500 rpm did not occur | One of four power windings in Stator is open | Repair/replace bad wire(s) AC1/AC2 or SL1/SL2 or replace Stator |
| Engine shuts down but overspeed above 4500 rpm did not occur | Main windings shorted to ground | Replace Stator |
| Engine shuts down but overspeed above 4500 rpm did not occur | Bad switch in Genistor | Replace Genistor |
| Engine shuts down but overspeed above 4500 rpm did not occur | No gate connection between CCG board and Genistor | Repair/replace bad wire(s) or replace bad CCG circuit board |
| Engine shuts down but overspeed above 4500 rpm did not occur | No connection between Genistor and Stator (AC1, AC2, SL1, SL2) | Repair or replace connecting wire(s) |
| Engine shuts down but overspeed above 4500 rpm did not occur | CCG board failure | Replace CCG circuit board |
| AC output turns off intermittently. Then, engine runs at idle for 5 seconds. Finally, AC turns back on and unit runs normally | CCG board failure | Replace CCG circuit board |
| Under heavy load, output turns off and engine speed drops to idle | CCG circuit board failure | Replace CCG circuit board |
| Engine cranks but won't start | Loss of DC power supply from the Engine Controller circuit board to the Ignition Module via Wire 14 | Inspect the Wire 14 connections at the 4-tab connector; check Wire 14; if DC voltage is NOT indicated, go to Test 21; if DC voltage is good, go on to Test 18 |
| Engine cranks but won't start | A failure in the Engine Controller circuit board has occured and DC power is not being delivered to the Wire 14 circuit | If DC voltage was NOT indicated in Test 17, but IS indicated now, repair, reconnect or replace Wire 14 between board and Ignition Module; if no DC voltage in Test 3 but good voltage now, replace Wire 14 between board and fuel pump; if there is no DC output from the circuit board to Wire 14, replace the Engine Controller circuit board |
| Engine won't start or starts hard and runs rough | Carburetion | Make sure the fuel tank has an ample supply of clean fresh gasoline (gasoline fuel systems) or gaseous fuel; make sure all shutoff valves are open; adjust the carburetor as outlined on Page 3.4-2; make sure the automatic choke is working properly and that the choke closes completely; adjust or repair carburetor or fuel system as necessary |
| Engine will not start, spark plug is WET | Overchoking; Water in fuel; Excessively rich fuel mixture; Intake valve stuck open | Adjust or repair carburetor or fuel system as necessary |
| Engine will not start, spark plug is DRY | Carburetor gasket(s) leaking; Fuel line plugged or shutoff valve not opening; Intake valve stuck closed; Inoperative fuel pump; Clogged fuel filter | Adjust or repair carburetor or fuel system as necessary |
| Engine will not start or starts hard and runs rough | A failure in the engine's mechanical system | Perform a compression check; if compression is poor, look for one or more of the following possible causes: Loose cylinder head bolts; Failed cylinder head gasket; Burned valves or valve seals; Insufficient valve clearance; Warped cylinder head; Warped valve stem; Worn or broken piston ring(s); Worn or damaged cylinder bore; Broken connecting rod |
| Engine starts, but then shuts down after startup | A problem could exist in either the generator computer system or in the engine DC control system | Isolate the CCG system using the test fixture; if the engine starts and shuts down, check engine oil level (if oil level is low, replenish as necessary; if oil level is NOT low, go to Test 26); if engine was shutting down after startup, but does not shut down during this test, the problem is in the CCG system, go to Test 27 |
| Engine starts, but then shuts down after startup | Low engine oil level | Replenish as necessary |
| Engine starts, but then shuts down after startup | Oil pressure switch | Replace oil pressure switch if it is bad |
| AC voltage was present at the Wires 66 and 77 terminals, but DC voltage is NOT present between the Battery Charge Rectifier's Wire 55 and frame ground | The Battery Charge Rectifier (BCR) is defective | |
| Engine starts, but the Stepper Motor does not move, and engine shuts down after several seconds | The CCG circuit board's micro-controller may not be operating | |
| Engine can be started, but shuts down after several seconds | A timing detection failure may have occurred (Timing winding, Wires TIM1, TIM2) | |
| Engine speed and output voltage are erratic under constant load, but the AC output does not turn off intermittently | Erratic timing detection may have occurred (Timing winding, Wires TIM1, TIM2) | |
| Engine cranks but won't start | A failure in the Engine Controller circuit board has occurred and DC power is not being delivered to the Wire 14 circuit | If DC voltage was NOT indicated in Test 17, but IS indicated now, repair, reconnect or replace Wire 14 between board and Ignition Module; if no DC voltage in Test 3 but good voltage now, replace Wire 14 between board and fuel pump; if there is no DC output from the circuit board to Wire 14, replace the Engine Controller circuit board |
| Engine will not start, spark plug is WET | Overchoking | Adjust or repair carburetor or fuel system as necessary |
| Engine will not start, spark plug is WET | Water in fuel | Adjust or repair carburetor or fuel system as necessary |
| Engine will not start, spark plug is WET | Excessively rich fuel mixture | Adjust or repair carburetor or fuel system as necessary |
| Engine will not start, spark plug is WET | Intake valve stuck open | Adjust or repair carburetor or fuel system as necessary |
| Engine will not start, spark plug is DRY | Carburetor gasket(s) leaking | Adjust or repair carburetor or fuel system as necessary |
| Engine will not start, spark plug is DRY | Fuel line plugged or shutoff valve not opening | Adjust or repair carburetor or fuel system as necessary |
| Engine will not start, spark plug is DRY | Intake valve stuck closed | Adjust or repair carburetor or fuel system as necessary |
| Engine will not start, spark plug is DRY | Inoperative fuel pump | Adjust or repair carburetor or fuel system as necessary |
| Engine will not start, spark plug is DRY | Clogged fuel filter | Adjust or repair carburetor or fuel system as necessary |
| Premature high temperature shutdowns | Early production units were equipped with a 265° F. switch | The 265° F. switch should be removed and replaced with the Part No. 94090 switch |
| Engine speed is maintained and no-load voltage is good. However, when load is applied output voltage drops and engine shuts down | Connections to Stepper Motor broken or disconnected | Repair or replace connections |
| Engine starts but Stepper Motor does not move. Shut down occurs after several seconds | Power supply winding in Stator shorted to ground (See NOTE 1) | Replace Stator |
| Priming function does not work | 15 amp fuse is bad | Replace bad fuse |
| Priming function does not work | No power to switch or low power | Check battery and battery circuit (Wires 13 and 15); recharge or replace battery as required; repair or replace loose, corroded or bad battery cables or wires as necessary |
| Priming function does not work | Fuel pump does not work | Replace pump if bad |
| Priming function does not work | Defective wire 14A | Repair or replace defective wire 14A |
| Priming function does not work | Defective primer switch | Replace switch if defective |
| Engine will not crank | 15 amp fuse bad | Replace bad fuse |
| Engine will not crank | Low or no battery power | Recharge or replace battery; repair or replace bad cable(s) |
| Engine will not crank | Starter contactor bad | Replace starter contactor |
| Engine will not crank | Starter motor bad | Replace starter |
| Engine will not crank | Engine Controller board power supply bad | Replace Engine Controller circuit board |
| Engine will not crank | Start-stop switch bad | Replace bad switch or bad wire 17 or bad ground wire as necessary |
| Engine cranks but will not start | Low fuel level | Replenish fuel supply |
| Engine cranks but will not start | Fuel filter bad | Replace filter |
| Engine won't start or starts hard and runs rough | Carburetion problem | Adjust or repair carburetor or fuel system as necessary |
| Engine will not start (spark plug WET) | Overchoking | Adjust or repair carburetor or fuel system as necessary |
| Engine will not start (spark plug WET) | Water in fuel | Adjust or repair carburetor or fuel system as necessary |
| Engine will not start (spark plug WET) | Excessively rich fuel mixture | Adjust or repair carburetor or fuel system as necessary |
| Engine will not start (spark plug WET) | Intake valve stuck open | Adjust or repair carburetor or fuel system as necessary |
| Engine will not start (spark plug DRY) | Carburetor gasket(s) leaking | Adjust or repair carburetor or fuel system as necessary |
| Engine will not start (spark plug DRY) | Fuel line plugged or shutoff valve not opening | Adjust or repair carburetor or fuel system as necessary |
| Engine will not start (spark plug DRY) | Intake valve stuck closed | Adjust or repair carburetor or fuel system as necessary |
| Engine will not start (spark plug DRY) | Inoperative fuel pump | Adjust or repair carburetor or fuel system as necessary |
| Engine will not start (spark plug DRY) | Clogged fuel filter | Adjust or repair carburetor or fuel system as necessary |
| Engine will not start or starts hard and runs rough (poor compression) | Loose cylinder head bolts | |
| Engine will not start or starts hard and runs rough (poor compression) | Failed cylinder head gasket | |
| Engine will not start or starts hard and runs rough (poor compression) | Burned valves or valve seals | |
| Engine will not start or starts hard and runs rough (poor compression) | Insufficient valve clearance | |
| Engine will not start or starts hard and runs rough (poor compression) | Warped cylinder head | |
| Engine will not start or starts hard and runs rough (poor compression) | Warped valve stem | |
| Engine will not start or starts hard and runs rough (poor compression) | Worn or broken piston ring(s) | |
| Engine will not start or starts hard and runs rough (poor compression) | Worn or damaged cylinder bore | |
| Engine will not start or starts hard and runs rough (poor compression) | Broken connecting rod | |
| Engine starts, but then shuts down after startup | Problem in the generator computer system (CCG system) | Go to Test 27 |
| Engine starts, but then shuts down after startup | Defective oil pressure switch or bad Wire 85 circuit | Replace oil pressure switch if defective or repair Wire 85 circuit as necessary |
| Engine starts, but then shuts down after startup | Oil pressure actually low | See Section 5.1, "ENGINE OIL SYSTEM" |
| Engine starts, but Stepper Motor does not move, and engine shuts down after several seconds | CCG circuit board's micro-controller may not be operating | |
| Engine starts, but Stepper Motor does not move. The engine accelerates uncontrollably and shuts down when engine speed exceeds 4500 rpm | Failure of the circuit board's Stepper Motor drive | |
| Engine starts, but Stepper Motor does not move. Engine appears to operate too slowly; engine is not able to handle the load and unit operates at low AC output voltage; after several seconds under load, AC output voltage is turned off (overload condition) | Failure of the circuit board's Stepper Motor drive | |
| Engine can be started, but shuts down after several seconds | Timing detection failure (Timing winding, Wires TIM1, TIM2) | |
| Engine speed and output voltage are erratic under constant load, but the AC output does not turn off intermittently | Erratic timing detection (Timing winding, Wires TIM1, TIM2) | |
| No AC voltage can be measured across Stator connections at the Battery Charge Rectifier (BCR) | Open circuit condition in Wire 66 (Brown) or Wire 77 (Brown) | |
| AC voltage is available to the Wire 66 and 77 terminals at the Battery Charge Rectifier, but no voltage or a low voltage is measured between the BCR's Wire 55 terminal and ground | Battery Charge Rectifier (BCR) is defective | Replace Battery Charge Rectifier |
| No AC voltage measured at Wires 66 and 77 terminals of the Battery Charge Rectifier with unit running | Open circuit exists in the wire 66 or 77 circuit | |
| AC voltage present at Wires 66 and 77 but DC voltage NOT present between Battery Charge Rectifier Wire 55 and frame ground | Battery Charge Rectifier (BCR) is defective | Replace Battery Charge Rectifier |
| Genistor fails resistance/continuity tests | Genistor defective | Replace Genistor |
| Battery charge winding resistance not within specification (Wires 66 to 55 = 0.037-0.042 Ohm; Wires 77 to 55 = 0.037-0.042 Ohm) | Stator Assembly defective | Replace Stator Assembly |
| Problem in AC generator system when other components tested good | CCG circuit board | Replace the CCG circuit board and check unit operation |
| Engine shutdown initiated by CCG board | Over-voltage | |
| Engine shutdown initiated by CCG board | Undervoltage (or overload) | |
| Engine shutdown initiated by CCG board | Overspeed above 4500 rpm | |
| Engine shutdown initiated by CCG board | Zero current failure | |
| Engine shutdown initiated by CCG board | Converter failure | |
| Engine shutdown initiated by CCG board | Microprocessor failure |
Fault codes and symptom→remedy steps extracted from this model’s service/owner documentation; verify against the official manual before servicing.
Documented causes: Loose cylinder head bolts; Failed cylinder head gasket; Burned valves or valve seals; Insufficient valve clearance. See the table for the matching fixes.
Documented causes: Out of fuel; Fuel pump is defective; Open Wire #14 from Eng. Control Bd.; Engine is flooded. See the table for the matching fixes.
Documented causes: 15 amp fuse is blown; Loose corroded or defective battery cables; Defective engine Start/Stop switch; Defective starter contactor. See the table for the matching fixes.