Broken, chafed, or corroded wiring in the clutch pedal position sensor B signal circuit; Loose or contaminated electrical connector at the clutch pedal position sensor B; Failed clutch pedal position sensor B internal open circuit; Poor ground connection shared by the clutch pedal position sensors; Water intrusion or debris in the sensor connector causing high resistance; Damage to the sensor from a misplaced floor mat or interference with the pedal linkage; Rarely, an internal fault in the powertrain control module driver circuit

DTC codes / P08xx · Transmission / P08B4

P08B4Clutch Pedal Position Sensor B Circuit/Open

Q: What does code P08B4 mean?

Clutch Pedal Position Sensor B Circuit/Open. P08B4 indicates that the powertrain control module has detected an open circuit or excessive resistance in the signal circuit for clutch pedal position sensor B, which is typically the second of two redundant sensors used to confirm clutch pedal movement. The computer monitors the expected voltage or signal return from this sensor and flags the code when the reading falls outside the normal range for the current pedal position.

P08B4 indicates that the powertrain control module has detected an open circuit or excessive resistance in the signal circuit for clutch pedal position sensor B, which is typically the second of two redundant sensors used to confirm clutch pedal movement. The computer monitors the expected voltage or signal return from this sensor and flags the code when the reading falls outside the normal range for the current pedal position.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaTransmission

Symptoms you may notice

Illumination of the check engine light or a dedicated clutch system warning light
Often no symptoms besides the warning light, especially if sensor A remains functional
Difficulty starting the engine because the clutch pedal must be depressed to engage the starter
Inconsistent or failed engagement of cruise control, which relies on clutch pedal status
Rough or jerky shifting if the engine management strategy uses clutch position for torque reduction
A stored code with no drivability complaint when the fault is intermittent or only affects the redundant signal

Common causes, most likely first

Broken, chafed, or corroded wiring in the clutch pedal position sensor B signal circuit
Loose or contaminated electrical connector at the clutch pedal position sensor B
Failed clutch pedal position sensor B internal open circuit
Poor ground connection shared by the clutch pedal position sensors
Water intrusion or debris in the sensor connector causing high resistance
Damage to the sensor from a misplaced floor mat or interference with the pedal linkage
Rarely, an internal fault in the powertrain control module driver circuit

How to diagnose and fix it

Verify the code with a scan tool and check for any related clutch or engine codes before touching hardware
Inspect the clutch pedal position sensor B connector and wiring for looseness, corrosion, or physical damage
Measure resistance and voltage on the sensor B signal circuit while exercising the clutch pedal to confirm an open or intermittent fault
Check the sensor ground circuit for excessive resistance using a voltage drop test under load
Replace the clutch pedal position sensor B if the circuit tests good but the sensor output is missing or erratic
Clear the code and perform a road test that includes clutch operation and cruise control activation to confirm the repair
If the fault persists after sensor and wiring repairs, diagnose the powertrain control module input circuit for an internal open

What the clutch sensor B code hides

Many vehicles use two clutch pedal position sensors for redundancy, so a failure of sensor B often produces no drivability change and the driver may never notice anything beyond the warning light.
A common misdiagnosis is replacing the clutch pedal position sensor B when the real problem is a worn clutch pedal pivot bushing that prevents the sensor from reaching its expected travel range.
Aftermarket floor mats or objects that block the clutch pedal from returning fully can set this code intermittently by keeping the sensor signal outside its learned range.
The code can be stored by a momentary open circuit caused by vibration or temperature changes, so a wiggle test of the harness while monitoring live data is often more revealing than a static resistance check.
Some vehicles share the sensor ground with the accelerator pedal or other pedal sensors, so a single bad ground point can set multiple pedal-related codes that seem unrelated.

Can I keep driving with P08B4?

The vehicle is generally safe to drive because the clutch still operates mechanically, but you should avoid relying on cruise control and be aware that the engine may not start if the remaining clutch sensor also fails. Have the circuit inspected soon to prevent a no-start condition.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.