Generac MMG45IF4 troubleshooting: 33 fault codes and symptom-cause-remedy entries from the manufacturer's own service documentation.
Generac MMG45IF4 — full specs, parts & maintenance.
| Code | Meaning | Cause | Remedy |
|---|---|---|---|
| 1049 VSCF | Overload RED Unit shuts down during operation. | Check the LEDs/Screen for alarms. Generator output is shorted or severely overloaded. Identify and clear the overload, and then restart. | |
| 1051 VSCF | High Battery YELLOW LED illuminated in any state. | Check the LEDs/Screen for alarms. Voltage supply to the AVR is high. If an external battery charger is in use, contact installing dealer to correct installation. If an external battery charger is NOT in use, contact Independent Authorized Servicing Dealer. | |
| 1052 VSCF | DC Overvoltage RED Unit shuts down during operation. | Check the LEDs/Screen for alarms. Probable causes are: 1) The generator was temporarily overloaded. 2) The output was temporarily shorted. Try to restart the unit. | |
| 1053 VSCF | Gate Fault RED Unit shuts down during operation or starting. | Check the LEDs/Screen for alarms. AVR is damaged. Contact Independent Authorized Servicing Dealer. | |
| 1055 VSCF | Phase Error RED Unit shuts down during starting. | Check the LEDs/Screen for alarms. An incorrect voltage and frequency has been detected during starting. Probable causes are: 1) Alternator damage. Contact Independent Authorized Servicing Dealer. 2) Generator has started into a severe load. Manually operate generator breaker and try to restart unit. If problem persists, remove load and attempt to restart unit again. 3) The engine may not be reaching its prescribed speed. Proceed as follows: •Verify stepper motor is moving and linkage is free. •Verify stepper motor is plugged in. •Verify gas pressure is within specified limits. | |
| 1056 VSCF | Undervoltage RED Unit shuts down during operation or starting. | Check the LEDs/Screen for alarms. The generator output voltage is too low. Probable causes are: 1) The load is too large. Remove load and attempt to restart unit. 2) Alternator or AVR damage. Contact Independent Authorized Servicing Dealer. | |
| 1057 VSCF | Overvoltage RED Unit shuts down during operation or starting. | Check the LEDs/Screen for alarms. Probable causes are: 1) The generator has been overloaded. Remove load and attempt to restart unit. 2) Generator has started into a severe load. Manually operate generator breaker and try to restart unit. If problem persists, remove load and attempt to restart unit again. | |
| 1058 VSCF | DC Undervoltage RED Unit shuts down during operation or starting. | Check the LEDs/Screen for alarms. The DPE winding supplies this voltage. 1) Alternator damage. Contact Independent Authorized Servicing Dealer. | |
| 1059 VSCF | Field Loss RED Unit shuts down during starting. | Check the LEDs/Screen for alarms. Unit detects no output voltage while starting. 1) Alternator damage. Contact Independent Authorized Servicing Dealer. | |
| 1061 VSCF | Field Loss RED Unit shuts down during operation. | Check the LEDs/Screen for alarms. Unit detects loss of output voltage while running. 1) Alternator damage. Contact Independent Authorized Servicing Dealer. | |
| 1065 | Overfrequency RED Unit shuts down during operation. | Check the LEDs/Screen for alarms. Probable causes are: 1) Overload. Remove load and attempt to restart unit. 2) RPM sensor has failed. Contact Independent Authorized Servicing Dealer. 3) Stepper motor problem. Contact Independent Authorized Servicing Dealer. | |
| 1066 VSCF | Speed mismatch RED Unit shuts down during Operation or starting. | Check the LEDs/Screen for alarms. Probable causes are: 1) Fuel problem (pressure loss). Check fuel supply and attempt to restart unit. 2) Large overload. Remove load and attempt to restart unit. 3) Throttle or engine problem. Contact Independent Authorized Servicing Dealer. | |
| HIGH TEMPERATURE | Unit shuts down during operation. | Check ventilation around the intake, exhaust and rear of generator. | Contact s Independent Authorized Servicing Dealer if no obstruction is found. |
| RPM SENSE LOSS | Unit was running and shuts down, attempts to restart. | Check the LEDs/Screen for alarms. | Clear alarm and remove household loads from the generator. Put back in AUTO and restart. If problem returns, contact Independent Authorized Servicing Dealer to investigate possible fuel issue. |
| Symptom | Cause | Remedy |
|---|---|---|
| Low Load indicator LED. • Indicates genset has operated at less than 30% capacity for more than 15 minutes. | Resolve by increasing electrical load. If unable to operate genset at more than 30% load, use a smaller generator. | |
| Lug Door Open indicator LED. | Resolve by closing lug-box door. If condition remains unresolved, inspect lug-box door safety switch for proper operation. | |
| Emergency Stop indicator LED. | Resolve by deactivating (pulling out) Emergency Stop switch. | |
| Shutdown indicator LED. | Resolve by resolving shutdown condition. | |
| Engine will not crank. | 1) Fuse blown. 2) Loose, corroded or defective battery cables. 3) Defective starter contact. 4) Defective starter motor. 5) Dead battery. | 1) Correct short circuit condition by replacing 7.5 Amp fuse. 2) Tighten, clean or replace as necessary.* 3) Tighten, clean or replace as necessary.* 4) Tighten, clean or replace as necessary.* 5) Charge or replace battery. |
| Engine cranks but will not start. | 1) Out of fuel. 2) Defective fuel solenoid (FS). 3) Defective spark plug(s). 4) Valve clearance needs adjustment. | 1) Replenish fuel / Turn on fuel valve. 2) * 3) Clean, check gap, or replace plug(s). 4) Adjust valve clearance. |
| Engine starts hard and runs rough. | 1) Air cleaner plugged or damaged. 2) Defective spark plug(s). 3) Fuel regulator not set. 4) Fuel pressure incorrect. 5) Fuel selector in wrong position. | 1) Check / replace air cleaner. 2) Clean, check gap, or replace plug(s). 3) Set fuel regulator. 4) Confirm fuel pressure to regulator is 10–12 in. water column (19–22 mm mercury) for LP, and 3.5–7 in. water column (7–13 mm mercury) for natural gas. 5) Move selector to correct position. |
| Generator is set to OFF, but the engine continues to run. | 1) Control board wired incorrectly. 2) Defective control board. | 1) Repair wiring or replace control board.* 2) Replace control board. |
| No AC output from generator. | 1) Main line circuit breaker is in the OFF (or OPEN) position. 2) Generator internal failure. | 1) Reset circuit breaker to ON (or CLOSED). 2) * |
| Unit consumes large amounts of oil. | 1) Oil tank is over filled with oil. 2) Engine breather defective. 3) Improper type or viscosity of oil. 4) Damaged gasket, seal or hose. | 1) Adjust oil to proper level. 2) * 3) See Engine Oil Recommendations. 4) Check for oil leaks. |
| Unit running in AUTO but no power in house. | Check Generator Disconnect circuit breaker. | Contact Independent Authorized Servicing Dealer if Generator Disconnect circuit breaker is in the ON position. |
| Unit will not start in AUTO with 2-wire start signal. | See if screen says unit not activated. | |
| Generator stalls when large load is supplied. | Total load is too big for the generator. Loads must be less than 10 kW or 2 hp when operating under 3600 rpm.Contact installing dealer to correct installation. | |
| Output voltage is low/high. | Voltage calibration incorrect. Contact Independent Authorized Servicing Dealer. | |
| Generator does not pull full power. | Current calibration incorrect. Contact Independent Authorized Servicing Dealer. | |
| Low Fuel Level Shutdown | 1. Check fuel level on the Liquid Crystal Display (LCD) window. Verify the unit is sitting level to ensure an accurate reading. 2. Check for leaks in fuel tank. The fuel tank should not run dry under normal circumstances. The engine controller will shut the engine down when there is five percent of fuel remaining in the tank. 3. If fuel level is good and no leaks are found, check the fuel level sender and the connecting wiring for damage. To check for continuity between the sender and the engine controller, remove the appropriate bolts from the control panel to access the inside of the control box. See the appropriate DC wiring diagram Wiring Diagrams for the proper path between the engine controller and the fuel level sender. | |
| Low Oil Pressure Shutdown | 1. Check engine oil level with the dipstick. The engine controller will shut the engine down when oil pressure is less than 20 psi (138 kPa). Add oil if required. 2. Visually inspect engine for oil leaks. 3. If oil level is good, restart the unit and verify the loss of oil pressure. Shut the engine down immediately if the oil pressure value does not read 5 psi (34 kPa) within five seconds. 4. Check oil pressure sender. To identify corrective action, see the troubleshooting section of the engine operator’s manual. | |
| Low Coolant Level Shutdown | 1. Allow engine to cool. 2. Check coolant level in the radiator. To access the radiator cap, remove the access panel from the top of the enclosure directly above the radiator. Add coolant until it is 3/4 in. (2 cm) below the filler neck. Secure the radiator cap back into its original position. 3. Inspect coolant hoses, engine block and water pump for visible leaks. 4. Check engine oil to verify no coolant has mixed with it (oil will appear milky if coolant is present). For additional information, see the engine operator’s manual. | |
| High Coolant Temperature Shutdown | 1. Check coolant level in the overflow jug. 2. Restart engine and read the coolant temperature to verify a high coolant temperature shutdown. Stop engine immediately if the coolant temperature is 230°F (110°C) or more. 3. Allow engine to cool. Add coolant to the overflow jug if it is low and check the level of coolant in the radiator. To access the radiator cap, remove the access panel from the top of the enclosure. |
Fault codes and symptom→remedy steps extracted from this model’s service/owner documentation; verify against the official manual before servicing.
Documented causes: 1) Fuse blown. 2) Loose, corroded or defective battery cables. 3) Defective starter contact. 4) Defective starter motor. 5) Dead battery.. See the table for the matching fixes.
Documented causes: 1) Out of fuel. 2) Defective fuel solenoid (FS). 3) Defective spark plug(s). 4) Valve clearance needs adjustment.. See the table for the matching fixes.
Documented causes: 1) Air cleaner plugged or damaged. 2) Defective spark plug(s). 3) Fuel regulator not set. 4) Fuel pressure incorrect. 5) Fuel selector in wrong position.. See the table for the matching fixes.