What it means
The ECM detects a circuit fault on the clutch position sensor b circuit. Reading cannot be used reliably for control.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
Clutch position sensor B reports the position of the B clutch mechanism so the control module can coordinate clutch operation and transmission shifts. P087A indicates an electrical fault in the B sensor circuit, making its position signal unreliable for that control.
Common causes
Most likely first.
- Sensor failed
- Wiring or connector fault
Symptoms
- Check engine or transmission warning light on
- Harsh, delayed, or missing shifts
- Possible limp mode (locked in one gear)
- Slipping or shuddering during gear changes
How to diagnose it
- Record freeze-frame data and check live clutch position sensor B data to see whether the signal is missing or implausible when the fault sets.
- Inspect sensor B and its connector for loose seating, damaged pins, corrosion, or contamination.
- Trace the B sensor wiring and look for breaks, chafing, or damage where the harness moves near the clutch or transmission.
- Use the wiring diagram to test sensor B's signal, reference, ground, and continuity against the manufacturer's specification.
- If the circuit is sound, test clutch position sensor B using the vehicle's specified procedure before replacing it.
Common fixes
- Secure the clutch position sensor B connector and clean poor terminal contact.
- Repair damaged wiring in the sensor B circuit.
- Replace clutch position sensor B if it fails testing with a sound circuit.
- Clear the fault and confirm B-position data responds consistently through clutch operation.
Can I keep driving?
Avoid hard acceleration, towing, and unnecessary trips if shifting is harsh, delayed, slipping, or the transmission enters limp mode. Unreliable clutch B position feedback can impair clutch engagement and continued slipping can damage the transmission.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.