Vehicle refuses to start charging and displays a ground connection error; Tesla app shows CP_a003

Safety: This is a wiring safety issue. Turn off the breaker and do not use the charger until the ground is verified and corrected by a qualified electrician.

• Check ground conductor: Confirm that a properly sized equipment grounding conductor is installed from the service panel to the Wall Connector ground terminal and is securely tightened.
• Inspect panel terminations: In the main or subpanel, verify the ground wire is landed on the correct ground bar and that the bar is bonded as required by local code.
• Look for corrosion or damage: Replace any corroded lugs or damaged ground conductors. Ensure all terminations are clean and tight.
• Test ground continuity: Use a multimeter or continuity tester (by a professional) to verify low‑resistance continuity between the Wall Connector ground terminal and the main service ground.
• Re‑energize and test: After corrections, restore power and attempt charging again. If CP_a003 persists, the internal ground sensing circuit on the control board may be defective and the Wall Connector may need replacement.