Clutch Position Sensor Circuit High
The P0808 code indicates that the engine or transmission control module has detected an unexpectedly high electrical voltage from the clutch position sensor circuit. This code is set when the sensor's output voltage exceeds the maximum threshold programmed by the manufacturer for a specified period.
This code is considered high severity because it can prevent the engine from starting or cause erratic transmission behavior. It should be diagnosed and repaired immediately to avoid being stranded.
Common symptoms
- Illuminated Check Engine Light
- Engine fails to crank or start
- Vehicle starts without depressing the clutch pedal
- Harsh or erratic transmission shifting
- Cruise control system is inoperative
Likely causes
- Faulty clutch position sensor
- Short to power in the clutch position sensor wiring
- Corroded, loose, or damaged electrical connectors
- Improperly adjusted clutch position sensor
- Mechanical issue with the clutch pedal assembly
- Faulty Powertrain Control Module (PCM) or Transmission Control Module (TCM)
What to check before replacing parts
Visually inspect the clutch position sensor, wiring harness, and connectors.
Look for: Look for frayed wires, melted insulation, corrosion in the connector pins, or physical damage to the sensor housing.
Connect a scan tool and monitor the clutch position sensor live data.
Look for: Observe the sensor voltage or percentage while pressing and releasing the clutch pedal; the reading should change smoothly without spiking or locking at maximum voltage.
Test the sensor's reference voltage and ground circuits using a digital multimeter.
Look for: Verify that the sensor is receiving the correct reference voltage (usually 5 volts) and has a solid ground; a missing ground can cause the signal voltage to read high.
Check the signal wire for a short to voltage.
Look for: Disconnect the sensor and the PCM/TCM, then measure voltage on the signal wire; any voltage present indicates a short to power in the harness.
Verify the mechanical adjustment and mounting of the clutch position sensor.
Look for: Ensure the sensor is securely mounted and properly aligned with the clutch pedal linkage, as a loose or misaligned sensor can produce inaccurate high readings.
This page explains the generic P0808 definition and is general reference information, not a diagnosis for your specific vehicle. Actual causes, severity, and repairs vary by make, model, engine, and mileage — always confirm with a scan tool and a qualified technician before replacing parts.
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