Code
P08B4
Generic
P — Powertrain
Clutch Pedal Position Sensor B Circuit/Open
Views:
UK: 25
EN: 33
RU: 22
AI status
Completed
Completed
100%
Causes
- Broken or disconnected wiring between sensor and PCM
- Corroded or pushed-back connector terminals
- Faulty clutch pedal position sensor (internal open)
- Blown fuse or loss of reference voltage/ground
- Intermittent short to battery or ground
- PCM input circuit fault (rare)
Symptoms
- MIL/Check Engine light illuminated
- Possible no-crank/no-start interlock or abnormal clutch-interlock behavior (if used to allow starting)
- Cruise control or start/stop functionality may be disabled
- Inconsistent or non-responsive clutch pedal-related functions
- Stored DTCs related to clutch pedal or input circuit faults
What to check
- Retrieve freeze frame and live data for clutch pedal sensors (A and B) with scan tool
- Visual inspection of sensor, mounting, wiring harness and connector for damage, corrosion or pin push-out
- Verify fuses and power/ground circuits for the sensor
- Backprobing sensor connector: check reference voltage (typically 5 V) and ground with key ON
- Measure sensor B output while moving pedal — should vary smoothly
- Compare Sensor A and Sensor B signals for consistency or expected inverse relationship (if applicable)
Signal parameters
- Reference supply: typically 5 V (verify vehicle-specific value)
- Signal output: typically an analog voltage that changes with pedal position (common range ~0.5 V to 4.5 V)
- At rest and full travel: signal should change smoothly without dropouts; sudden jump to 0 V or ~Battery voltage indicates open or short
- Resistance: if sensor is a potentiometer, resistance should change smoothly across travel (measure with harness disconnected)
- Frequency: not applicable for simple analog sensors; hall sensors produce steady DC voltage proportional to position
Diagnostic algorithm
- Read and record DTCs and freeze-frame data. Note operating conditions when code set.
- Inspect sensor connector and wiring for damage, corrosion, chafing, or rodent chew. Repair any obvious faults.
- With ignition ON (engine off), backprobe connector: verify reference voltage and ground are present and stable.
- Measure sensor B output voltage while an assistant slowly operates the clutch pedal. Confirm voltage changes smoothly across pedal travel and remains within manufacturer range.
- Wiggle wiring and connector while monitoring voltage to detect intermittent opens or shorts.
- If open/no signal: disconnect harness and check continuity between sensor pin and PCM pin. Repair any open circuits.
- If reference or ground missing, trace and repair upstream fuse, relay, or wiring fault.
- If wiring and power/ground are good but sensor output is invalid or does not change, replace clutch pedal position sensor.
- After repairs clear codes, verify with functional test and road test. Re-scan for any reoccurrence or related codes.
- If problems persist after sensor and wiring checks, consider PCM input circuit diagnosis or replacement per manufacturer's procedures.
Likely causes
- Open or damaged wiring/connector at the clutch pedal sensor
- Corroded or loose connector pins
- Failed clutch pedal position sensor B
- Loss of reference voltage or ground to the sensor
Fault status
Status
Clutch Pedal Position Sensor B Circuit/Open — PCM has detected an open or out-of-range signal on the CPP Sensor B input. The fault may be intermittent if caused by wiring or connector issues.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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