What does it mean?
C1097 is a Chassis (ABS, traction control, steering) fault code. It indicates: ABS Hydraulic Pump Motor 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 pump runs continuously or whines with the ignition on and the vehicle stationary
- ABS and stability control lamps on
- Relay or connector gets hot, sometimes with a smell of melted plastic
- Battery goes flat overnight from the constant pump load
- ABS regulation unavailable during hard braking
- Fuse blows once the overheated circuit finally shorts
Likely causes
- Pump motor control wire chafed onto a permanently live circuit inside the harness
- Pump relay contacts welded closed, so the motor is powered all the time
- Moisture or corrosion bridging a live pin to the motor pin in the hydraulic unit connector
- Damaged harness at the fuse box where several heavy feeds run side by side
- Incorrect repair or added accessory wiring tapped into the ABS supply
- Shorted driver inside the ABS control module holding the circuit high
How to fix it
- Pull the ABS pump relay and note whether the motor stops running
- Bench test or swap the relay to check for welded contacts
- Unplug the hydraulic unit connector and check for voltage on the motor pin with the key on
- Inspect the harness between the fuse box and the modulator for melted insulation and chafe points
- Open and dry the connector, then clean corrosion that could bridge adjacent pins
- Repair the shorted harness section and replace any heat damaged relay or connector body
- Replace and programme the ABS control module only if the module itself holds the circuit high