E4
MUSTART
Ground Fault / Leakage Current Detected
Charger displays “E4” and refuses to charge; sometimes appears immediately when plugging into the EV.
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Moisture inside J1772 connector, damaged insulation in charging cable, ground fault in vehicle’s onboard charger, internal leakage current sensor fault on control board
How to Fix / Troubleshooting
Safety warning: Ground faults can be dangerous. If you see sparks, smell burning, or the cable jacket is damaged, stop using the charger immediately.
- Disconnect and dry: Unplug the charger from the wall and from the vehicle. If the connector or cable is wet (rain, snow, car wash), allow it to dry completely indoors for at least 24 hours.
- Inspect cable and plug: Look for cuts, abrasions, or crushed sections along the MUSTART cable. Check the J1772 handle for cracks or melted plastic. Do not use the charger if any damage is visible.
- Test with another EV (if possible): If E4 only occurs with one vehicle, the fault may be in that EV’s charging system. Consult the vehicle manufacturer.
- Persistent E4: If E4 appears with multiple vehicles and the cable looks intact and dry, the internal leakage detection circuit on the main control board may be faulty. The charger should be professionally serviced or replaced.
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Repair Difficulty
Hard
4/5
Required Part
Charging Cable Assembly or Main Control Board (Ground Fault Sensor)
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