Powertrain, generic · Transmission

P08B4 Clutch Pedal Position Sensor B Circuit/Open

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

Some manual cars read the clutch pedal with two independent sensors so a single failure can be detected; Ford's 2020–23 gasoline OBD summary describes such a dual PWM layout. Sensor B is the second channel. P08B4 is the general circuit or open-wire fault of that second sensor. No manufacturer documents this code publicly: Ford uses only P08B6/P08B7 for sensor B plus P08B9 for the A/B comparison, and GM's tables cover sensor A alone. The code therefore rests on CARB's requirement to monitor such inputs for circuit faults. Sensor A's counterpart is P08A7. As long as sensor A is healthy the controller can usually still judge the pedal, but start-stop is often locked out until the fault is fixed.

Likely causes

Loose connector or broken wire on the sensor B channel
Internal fault in clutch pedal position sensor B (often a shared housing with sensor A)
Missing supply or ground for sensor B
Faulty sensor B input in the engine control module

Symptoms

  • Warning lamp on
  • Start-stop disabled
  • Correlation code P08B9 may be stored as well

Repair estimate

DifficultyEasyDIY possible
Parts and labour€50–300
Time0.3–1.5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

clutch pedal position sensor bwiring harnessecm

Related codes

P08B5P08B6P08B7P08B8P08B9P08A7

References: law.cornell.edu, fordservicecontent.com.