GM EV home charger displays E04 and will not charge; often occurs after installation or after electrical work in the home.

Safety first: Turn OFF the charger breaker. Only a qualified electrician should remove the charger cover or measure live voltage.

Homeowner checks:

• Confirm breaker rating: Verify that the GM charger is on the correct double‑pole breaker size specified in the installation manual (commonly 40A or 60A, depending on model).
• Check for recent changes: If E04 started after panel work or charger relocation, inform your electrician; miswiring is common after modifications.

Electrician checks (do not perform unless qualified):

• Measure line‑to‑line voltage at the charger input; it should be within the GM‑specified range (typically ~208–240 VAC).
• Inspect and tighten lugs on the charger’s line terminals and ground bar per GM torque specs.
• Verify that no neutral is incorrectly tied to the charger’s line terminals on hardwired models.

If voltage is consistently out of range or unstable, the issue may be with the utility supply or the home’s distribution panel. Do not continue using the charger until the supply is corrected, as over/undervoltage can damage the internal power module.