P08B5

What it means

P08B5 is a generic powertrain code meaning the engine or transmission control unit has found the signal from clutch pedal position sensor B is out of its expected range or does not agree with other inputs. The signal is still present, but it does not make sense, for example it does not change as expected when the pedal is pressed and released, or it disagrees with sensor A or the clutch switch. Exact sensor layout and plausibility checks vary by model and engine.

Symptoms

• Engine fails to start or only starts with the pedal pressed hard or held down
• Cruise control not working or cutting out
• Stop-start system disabled or behaving erratically
• Hesitation, surging or poor response when changing gear
• Hill start assist not working on cars fitted with it
• Engine warning light on with a stored fault

Possible causes

• Clutch pedal position sensor B out of adjustment, loose or worn mounting so its reading is offlikely
• Faulty clutch pedal position sensor B giving an erratic or drifting signallikely
• Damaged wiring, poor connector contact or corrosion in the sensor B circuit (signal, reference or earth)likely
• Worn or damaged pedal assembly, bracket or sensor actuator so the pedal travel is not read correctlypossible
• Disagreement with a second clutch sensor or switch because that device or its circuit is faultypossible
• Low or unstable supply voltage or earth fault affecting sensor readingspossible
• Fault in the control unit or outdated software calibration, where a known issue is documented for the modelrare

How to diagnose

1. Read all stored codes and freeze frame data, and note whether other clutch, brake or cruise control codes are also present
2. Visually inspect the pedal area, sensor, bracket and linkage for damage, looseness, spilled liquid or interference from carpet or objects
3. Inspect the wiring and connector for sensor B for chafing, pushed-out pins, corrosion and water ingress
4. With a scan tool, watch the live clutch sensor B value (and sensor A or switch if fitted) while slowly pressing and releasing the pedal, and look for dropouts, steps or values that do not match
5. Check the sensor's reference voltage, signal and earth at the connector against the manufacturer's specification for that model
6. Check the sensor's mounting and adjustment, and confirm the pedal returns fully to its rest position
7. Perform a voltage drop test on the circuit and check the battery and charging condition
8. Check for applicable service bulletins or software updates for the model before replacing the control unit

How to fix

• Refit, secure or adjust the sensor and its mounting to the manufacturer's procedure
• Replace the clutch pedal position sensor B if its signal is erratic or out of specification
• Repair or replace damaged wiring and clean or renew faulty connector terminals
• Replace a worn pedal assembly, bracket or actuator part
• Repair the faulty second sensor, switch or circuit if the disagreement originates there
• Update the control unit software only where an outdated calibration is a documented cause, then clear the code and road test to confirm it does not return

Can I keep driving?

Nearby codes

• P08B4GenericClutch Pedal Position Sensor B Circuit/Open
• P08B6GenericClutch Pedal Position Sensor B Circuit Low