BMW Wallbox displays E04; charging stops shortly after plug-in, LED ring red

Safety first: Only qualified personnel should measure mains voltage inside the Wallbox. Turn off the breaker before opening any covers.

• Check supply voltage: Have a licensed electrician measure line-to-line and line-to-neutral voltages at the Wallbox input terminals. Compare with the rating plate (e.g., 230/400 V).
• Inspect terminals: With power off, verify all phase and neutral conductors are fully inserted and tightened to the torque specified in the BMW installation manual. Look for discoloration or signs of arcing.
• Confirm grid type: Ensure the Wallbox is configured for the correct grid (single-phase vs three-phase) if the model supports configuration. Incorrect wiring can trigger E04.
• Check upstream devices: Overvoltage may be caused by a faulty transformer or supply issue. If measured voltage is consistently high, contact your utility provider.

If supply voltage is within spec and connections are sound, the internal voltage sensing circuit or control board may be defective. In that case, arrange replacement of the BMW Wallbox main control board through an authorized service partner.