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DTC codes / P08xx · Transmission / P087C

P087CClutch Position Sensor B Circuit Low

P087C indicates that the powertrain control module (PCM) has detected a low voltage signal on the circuit for clutch position sensor B, which is used to monitor the travel or engagement point of the clutch in a manual or dual-clutch transmission. The PCM expects a voltage within a specific range as the clutch pedal moves, and a sustained low reading tells the module that the sensor circuit is shorted to ground, has excessive resistance, or the sensor itself has failed.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaTransmission

Symptoms you may notice

  • Illumination of the check engine light or transmission warning light, often with no other noticeable symptoms
  • Difficulty engaging gears or a clutch pedal that feels inconsistent or sticks
  • The engine may hesitate or stumble when pulling away from a stop, as the PCM misjudges clutch engagement
  • In some vehicles, the engine may refuse to start because the clutch pedal position is not recognized
  • Poor fuel economy or altered throttle response due to incorrect load calculations
  • Intermittent limp mode or reduced power if the fault affects torque management strategies

Common causes, most likely first

  1. Faulty clutch position sensor B, worn or internally shorted
  2. Damaged or chafed wiring harness between the sensor and the PCM, causing a short to ground
  3. Corroded, loose, or disconnected electrical connector at the sensor or PCM
  4. Water intrusion or contamination in the sensor connector or harness
  5. Mechanical binding or incorrect clutch pedal adjustment that forces the sensor out of its normal range
  6. PCM internal fault or software issue misinterpreting a valid signal (rare)

How to diagnose and fix it

  1. Verify the code with a scan tool and check for any related pending or history codes in the transmission and engine modules
  2. Inspect the clutch position sensor B connector and wiring for corrosion, chafing, or loose pins, and repair as needed
  3. Measure reference voltage and ground at the sensor connector with a digital multimeter (DMM) to confirm the circuit integrity
  4. Back-probe the signal wire at the PCM and compare the voltage with the sensor output while slowly pressing the clutch pedal
  5. Test the sensor with a multimeter for a smooth resistance or voltage sweep through its full travel, replacing it if the signal drops out or shorts
  6. Check clutch pedal mechanical operation and adjustment, ensuring the sensor is not being over-traveled or binding
  7. Clear the code and perform a road test with live data to confirm the signal returns to normal and the code does not reset

Clutch sensor B low voltage traps

  • A low voltage code often results from a short to ground in the harness where it rubs against the clutch pedal bracket or firewall, not from a failed sensor.
  • Technicians sometimes replace the clutch position sensor only to find the connector pins are pushed back or corroded, so always perform a wiggle test on the harness while watching live data.
  • On some vehicles, a weak or failing battery can cause the PCM to misread sensor voltages during cranking, setting a low voltage code that disappears after a battery replacement.
  • The clutch position sensor B may share a ground circuit with other sensors, so a bad ground elsewhere can pull the signal low and set this code without any fault in the sensor itself.
  • A misadjusted clutch pedal stop can physically force the sensor into its lowest voltage position, mimicking an electrical short and leading to unnecessary parts replacement.

Can I keep driving with P087C?

You can usually drive the vehicle with this code, but avoid aggressive clutch operation and be prepared for possible stalling or difficulty engaging gears. If the engine fails to start or the clutch feels unsafe, stop driving and have the fault diagnosed promptly.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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