What does it mean?
C1165 is a Chassis (ABS, traction control, steering) fault code. It indicates: ABS Hydraulic Valve Power Relay Circuit Short to Ground .
Symptoms
- ABS lamp on and stays on from key-on, generally with the traction and stability lamps
- ABS function is disabled, so the wheels can lock and the pedal does not pulse under emergency braking
- Braking still works normally in every other respect but the safety net on slippery surfaces is gone
- ABS fuse blowing repeatedly, or an audible chatter from the relay area instead of one clean click
- Hill-start assist and electronic brake force distribution may drop out at the same time
Likely causes
- Insulation worn through where the relay wiring passes a body bracket, clip or the edge of the ABS hydraulic unit
- Corrosion or standing water in the engine bay fuse and relay box bridging the circuit to the box housing
- Relay failed internally with its winding shorted to the metal case
- Harness crushed or pinched during previous suspension, engine mount or accident repair work in the same area
- Damaged loom under the battery tray or along the inner wing where fluids and heat collect
- ABS module output driver failed short, holding the circuit at ground with the key on
- Poorly insulated splice from a previous repair or an aftermarket accessory tapped into the ABS supply
How to fix it
- Check the ABS fuses first — a short to ground normally takes a fuse or makes the relay chatter, and that narrows the search quickly
- Read all chassis codes; a whole family of valve and relay codes at once usually means one common power problem
- Remove the relay and inspect the socket, the box interior and the terminals for water, salt and corrosion
- With the relay removed and the ABS module unplugged, measure resistance from the relay control terminal to chassis ground; a near zero reading confirms the short
- Open the loom along its whole run from the fuse box to the hydraulic unit and check every clip, bracket and flex point for chafe marks
- Repair damaged wiring with soldered, sealed joints and reroute it away from the point that caused the wear
- Replace the relay if it tests shorted internally, and consider the ABS module only after the harness is proven clean