Faulty clutch position sensor (internal failure or low output); Signal wire shorted to earth or chafed against bodywork or the gearbox; Corroded, loose or water-damaged connector or terminals at the sensor; Open circuit or high resistance in the sensor supply or reference voltage wire; Sensor or magnet misaligned or damaged after clutch or gearbox work; Faulty control unit (gearbox, engine or body module) driver or input; Outdated control unit software where the manufacturer has published a fix for this fault.

P087C

Clutch Position Sensor B Circuit Low.

Generic
Powertrain
Generic code
Medium severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
8: AreaTransmission
7C: FaultThe specific fault in that area

What it means

P087C means the control unit has seen the signal from clutch position sensor B at a voltage lower than its expected range. The sensor may be on a manual car (start-inhibit or stop-start logic) or on an automated manual or dual-clutch gearbox, where it feeds clutch control. The cause is usually a wiring, connector, supply or sensor fault, and which module owns the sensor depends on the model.

Symptoms

Warning light on, possibly with a transmission or gearbox warning message
Car will not start, or starts only with the clutch pedal pressed hard or not at all
Stop-start system disabled
Rough, jerky or delayed gear changes on automated manual or dual-clutch gearboxes
Limp mode or gearbox stuck in one gear
Cruise control or hill-hold not working

Possible causes

Faulty clutch position sensor (internal failure or low output)likely
Signal wire shorted to earth or chafed against bodywork or the gearboxlikely
Corroded, loose or water-damaged connector or terminals at the sensorlikely
Open circuit or high resistance in the sensor supply or reference voltage wirepossible
Sensor or magnet misaligned or damaged after clutch or gearbox workpossible
Faulty control unit (gearbox, engine or body module) driver or inputrare
Outdated control unit software where the manufacturer has published a fix for this faultrare

How to diagnose

Read all stored codes and freeze frame data, noting mileage, speed and conditions, and check for related supply voltage or clutch codes
Check the battery condition and charging voltage, as low system voltage can upset sensor readings
Look over the sensor, wiring and connector for chafing, oil or water ingress, corrosion and bent or pushed-back pins
Check live data for the clutch position reading while pressing and releasing the pedal (or operating the clutch), and see whether it is stuck low or drops out
Using the wiring diagram for the model, check the sensor supply, signal and earth with a multimeter, and test the signal wire for a short to earth
Wiggle-test the harness and connector with live data running to find intermittent faults
Check the sensor mounting, air gap and target or magnet for damage or misalignment
Check for manufacturer software updates or technical bulletins applicable to the vehicle

How to fix

Replace the clutch position sensor if it is out of specification or fails the tests, and carry out any learn or adaptation procedure the model needs
Repair or replace damaged wiring, correcting any short to earth or open circuit
Clean, repair or replace corroded or damaged connector terminals and seal them against moisture
Correct sensor mounting or alignment and refit any damaged magnet or target
Update the control unit software only where the manufacturer lists it as a fix for this fault
Replace the control unit only after wiring, supply and sensor are proven good

Can I keep driving?

Medium severity

The car may be driveable, but it could refuse to start, lose stop-start or go into limp mode without warning. Have it checked soon, and avoid long journeys until it is fixed, especially if gear changes feel harsh or erratic.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.