What does it mean?
C1215 is a Chassis (ABS, traction control, steering) fault code. It indicates: ABS Hydraulic Valve Power Relay Circuit Short to Battery . This is a standardised OBD-II code. The technical definition is the same regardless of the make or model of vehicle, although specific causes and symptoms can vary between vehicles.
Symptoms
- ABS and stability lamps on at key-on and staying on
- Valve relay remains energised with the key off, sometimes with a faint buzz from the hydraulic unit
- Parasitic battery drain and a flat battery after the vehicle stands
- ABS, traction control and stability control unavailable
- Fuses in the ABS circuit blowing on some vehicles
Likely causes
- Relay control wire chafed against a permanently live cable, such as the alternator or starter feed
- Water or corrosion bridging pins inside the relay box, connecting the control line to a live pin
- Relay contacts welded closed so battery voltage is fed back into the circuit
- Aftermarket accessory, alarm or trailer wiring spliced into the ABS supply harness
- Wrong relay fitted, with a different pin layout or without the correct internal diode
- Damaged high side driver inside the ABS module
How to fix it
- Disconnect the ABS module connector and measure the control terminal against ground with the key off and again with the key on; voltage present confirms the short to battery
- Inspect the harness where it runs beside charging and starter cables for rub-through and melted insulation
- Open the relay box, dry it, and check for corrosion or water tracks bridging the pins
- Remove the relay and check for stuck or welded contacts, and confirm the part number matches
- Disconnect any added accessory wiring in the area and retest the circuit
- Repair the damaged section and re-route it away from live cables, then confirm the drain is gone
- Replace the ABS module only after the harness is proven clean