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P codepowertrainMedium severity

P087DClutch Position Sensor "B" Circuit High

The clutch position sensor "B" circuit voltage is stuck above its valid range, typically from an open ground, a short to voltage, or an open sensor.

Definition

The TCM expects the clutch position sensor "B" output to stay within a defined voltage window across the clutch's full travel. P087D sets when the signal exceeds the maximum plausible voltage, which points to an open sensor ground letting the signal float to the reference rail, a signal wire crossed with battery or reference voltage, or an internally open sensor element. With clutch position unknown, the TCM restricts control of that clutch — expect harsh engagement or a disabled clutch path, gear restrictions or limp-home on dual-clutch transmissions, and a transmission warning lamp.

Common causes

  • Open sensor ground circuit
  • Signal wire shorted to 5V reference or battery voltage
  • Clutch position sensor failed open internally
  • Corroded connector terminal creating an open in the signal or ground path
  • Harness damage from heat or abrasion
  • TCM input circuit failure (rare)

Common misdiagnoses

  • Replacing the sensor when the ground wire is open
  • Replacing the clutch actuator assembly
  • Replacing the TCM/mechatronic unit before circuit testing
  • Replacing the clutch for engagement harshness

Troubleshooting steps

  1. 1.Confirm the signal is railed high

    Back-probe the signal wire key-on; a reading pinned at 5V or battery voltage regardless of commanded clutch position confirms the high-circuit fault.

  2. 2.Check the sensor ground

    Measure voltage from the sensor ground pin to battery negative key-on; more than 0.1V means a poor or open ground, the most common reason a ratiometric sensor rails high.

  3. 3.Rule out a short to voltage

    With the sensor unplugged and key on, verify the signal wire is not carrying battery voltage; 12V on a 5V signal circuit indicates crossed wiring in the harness.

  4. 4.Test the sensor element

    With supply and ground verified good at the connector, an output still stuck high condemns the sensor; substitute a known-good unit or check element resistance per the service manual.

  5. 5.Adapt and road test

    Perform the clutch relearn after repair and confirm the measured position sweeps smoothly from released to applied with no code reset.

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