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DTC codes / P08xx · Transmission / P08B8

P08B8Clutch Pedal Position Sensor B Circuit Intermittent/Erratic

P08B8 means the powertrain control module (PCM) has detected an intermittent or erratic signal from the clutch pedal position sensor B circuit, which is the second of two redundant sensors used to confirm clutch pedal travel. The PCM expects a smooth, predictable voltage change as the pedal moves, and it flags this code when the signal jumps, drops out, or fails to correlate with sensor A or the pedal's expected range.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaTransmission

Symptoms you may notice

  • The check engine light or a clutch-related warning lamp illuminates on the dashboard.
  • The engine may hesitate, stumble, or cut out when you press or release the clutch pedal.
  • Cruise control may disengage unexpectedly or refuse to engage at all.
  • The engine may not start unless the clutch pedal is pressed very firmly or at a specific point in its travel.
  • You may notice a brief loss of power or a surge during gear changes.
  • Often no symptoms besides the warning light, especially if sensor A still provides a usable signal.

Common causes, most likely first

  1. A worn or contaminated clutch pedal position sensor B, often due to dirt, moisture, or internal contact wear.
  2. A loose, corroded, or damaged electrical connector at the sensor or along the wiring harness.
  3. Chafed, pinched, or broken wires in the sensor B circuit, particularly near the pedal assembly where movement occurs.
  4. A misadjusted or binding clutch pedal linkage that prevents the sensor from sweeping its full range smoothly.
  5. An intermittent open or short in the sensor B signal circuit caused by heat, vibration, or water intrusion.
  6. A failing PCM or a software issue in the PCM that misinterprets a valid sensor signal, though this is less common.
  7. Aftermarket or incorrectly installed clutch components that alter pedal geometry and sensor travel.

How to diagnose and fix it

  1. Use an OBD-II scan tool to read the freeze-frame data and confirm P08B8 is the only clutch-related code stored.
  2. Visually inspect the clutch pedal position sensor B, its connector, and the wiring harness for looseness, corrosion, or damage.
  3. Back-probe the sensor B signal wire and watch the voltage on a multimeter or oscilloscope while slowly pressing and releasing the clutch pedal.
  4. Compare sensor B voltage against sensor A voltage throughout the pedal travel to identify a dead spot, jump, or dropout.
  5. Check the clutch pedal linkage and adjustment to ensure the pedal moves freely and the sensor reaches both ends of its range.
  6. Repair or replace the faulty sensor, connector, or wiring section, then clear the codes and verify the signal is smooth and consistent.
  7. Perform a road test with the scan tool recording live data to confirm the code does not return under driving conditions.

Why clutch sensor B fails intermittently

  • A common oversight is replacing sensor B without checking the pedal linkage, because a worn bushing or bent bracket can make a good sensor produce an erratic signal.
  • The code can set from a momentary voltage glitch that never appears during a static test, so live data recording during a test drive is often the only way to catch it.
  • Sensor B is usually the redundant channel, so the vehicle may drive almost normally and the only clue is the stored code or a slight change in clutch engagement feel.
  • Water intrusion into the connector after a car wash or heavy rain is a frequent cause of intermittent clutch sensor codes that disappear in dry weather.
  • A failing clutch pedal position sensor A can also trigger P08B8 because the PCM cross-checks both sensors and flags B when the correlation between them falls outside the expected range.

Can I keep driving with P08B8?

You can usually drive the vehicle to a repair shop, but avoid aggressive clutch use and long trips because an erratic signal can cause the engine to cut out or the cruise control to drop unexpectedly. If the engine stalls repeatedly or refuses to start, stop driving and have the fault diagnosed promptly.

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.

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