High Voltage Contactor Open, Drivetrain Disabled

Common Symptoms

• Car displays a red warning on touchscreen and will not accelerate or move at all
• Touchscreen shows 'Car needs service' or 'Unable to drive' message
• HVP_a005 appears in fault log via Scan My Tesla or TM-Spy
• 12V accessories, lights, and touchscreen may still function normally while the drivetrain is dead
• Car may have shut down suddenly while driving, coasting to a stop
• Charging may be blocked or the charge port light pulses amber without starting a session
• HVAC blower and climate may stop working along with the loss of drive power

Probable Causes (Ranked by Likelihood)

• Pyro fuse (manual service disconnect or automatic pyrofuse) triggered by a hard fault or crash event, opening the high voltage loop permanently Very Likely
• High voltage contactor failed open or welded in a previous fault, causing HVP to lock out the system as a protective response Very Likely
• BMS detected a cell-level fault such as overvoltage, undervoltage, or thermal runaway precursor, commanding contactors to open Likely
• Isolation fault detected on the HV bus (water intrusion, damaged wiring, or insulation breakdown), causing HVP to open contactors for safety Likely
• Service mode or manual shutdown via the Tesla service menu left contactors in the open state and was not properly cleared Possible
• CAN communication loss between HVP and BMS or GCON, causing HVP to default to a safe open-contactor state Possible
• Low 12V auxiliary battery voltage causing the HVP controller to lose sufficient power to command contactor closure Less Likely

Step-by-Step Diagnostic Procedure

1. Check the 12V battery first. If the 12V system is below 11V, the HVP module cannot reliably command the contactors. Jump or charge the 12V battery and see if the fault clears on reboot. Reboot the car by holding both scroll wheel buttons until the screen goes dark.

2. Connect a Scan My Tesla-compatible adapter (OBDLink MX+ or Veepeak) and open Scan My Tesla or TM-Spy. Pull the full fault log. Look for companion codes from BMS (cell fault), DI (inverter fault), or VCFRONT that fired before HVP_a005. The code that fired first tells you the root cause.

3. Inspect the manual service disconnect (MSD) location. On Model S and Model X this is under the rear seat or cargo floor. On Model 3 and Model Y it is not user-accessible, but if the car was recently in a shop, confirm the orange high-voltage connector was fully reseated after any service.

4. Check for any physical trauma. If the car was in a collision, even a minor rear or undercarriage impact, the pyrofuse may have blown. A blown pyrofuse is a one-way device and cannot be reset. It requires replacement by a technician with access to Tesla Toolbox 3 to re-enable the HV system afterward.

5. Look for water intrusion signs around the battery pack edges, charge port area, and HV cable routing. Moisture causing an isolation fault will keep HVP locked out even after the water dries. Look for corrosion or moisture-related DTCs in the fault log.

6. Check whether the car entered service mode recently. Navigate to the Tesla service menu (available via touchscreen long-press on some older firmware versions, or via Toolbox 3 at a shop). If the HV system was manually disabled for service, it requires a deliberate re-enable sequence. This step typically needs Tesla Toolbox 3.

7. If no obvious cause is found and the 12V battery is healthy, this fault almost always requires Tesla Toolbox 3 to read live HVP data, confirm contactor state, run the HV system re-engagement sequence, and clear the lockout. This is a dealer-level or certified EV shop procedure. Do not attempt to manually jump the HV contactors.

Frequently Asked Questions