Safety first: Turn OFF the breaker before opening the charger. Only a qualified person should measure live voltages.

Step 1 – Confirm breaker rating: Verify that the charger is on the correct amperage breaker as specified in the Chevrolet charger installation manual (e.g., 40 A, 50 A, or 60 A 2-pole breaker for 240 V models).
Step 2 – Inspect wiring connections: With power OFF and cover removed, check that L1, L2, and ground are securely tightened in the charger’s terminal block. Look for discoloration or melted insulation.
Step 3 – Measure voltage (electrician): Have an electrician measure line-to-line and line-to-ground voltages at the charger input while under light load. Values must be within the range specified by Chevrolet (typically around 208–240 V for Level 2).
Step 4 – Check for shared circuits: Ensure the charger is on a dedicated circuit. Other large loads on the same circuit can cause voltage sag and trigger E04.
Step 5 – Correct wiring errors: If the charger is mistakenly wired to 120 V or to a multi-wire branch circuit without proper handle ties, have an electrician correct this immediately.

Charger shows E04 and the vehicle reports ‘Incorrect Voltage’ or ‘Charging Power Reduced’.

Possible Causes