C1239: ABS Hydraulic Pressure Differential Switch Input Open Circuit
MediumChassisAnti-Lock Brakes
What does C1239 mean?
C1239 is a diagnostic trouble code indicating "ABS Hydraulic Pressure Differential Switch Input Open Circuit". This means there is an electrical break in the anti-lock brakes wiring — a connector may be unplugged, a wire broken, or a component has failed internally. The ECU detected no signal where it expected one.
Common causes
- Damaged or corroded wiring harness
- Loose or disconnected electrical connector
- Failed anti-lock brakes sensor or actuator
- Blown fuse in the related circuit
- Poor ground connection
What should you do?
Schedule a diagnostic appointment at your earliest convenience. The vehicle is generally safe to drive short distances, but the underlying issue should be addressed to prevent it from worsening.
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Code C1239 can mean different things depending on your vehicle. TorqueBot gives you a diagnosis specific to your make, model, and year.