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DTC codes / P07xx · Transmission / P07C8

P07C8Intermediate Shaft Speed Sensor B Circuit High

P07C8 means the powertrain control module (PCM) has detected a high-voltage signal on the intermediate shaft speed sensor B circuit, which typically indicates an open circuit, a short to voltage, or a sensor that is not producing the expected signal. The PCM compares this signal against other speed inputs and sets the code when the voltage stays above the calibrated threshold for a set time.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaTransmission

Symptoms you may notice

  • Illumination of the check engine light, often with no other noticeable symptoms
  • Harsh or erratic shifting because the transmission cannot accurately determine intermediate shaft speed
  • Transmission may enter limp mode or fail to shift into certain gears
  • Speedometer or tachometer readings may become inaccurate or intermittent
  • A stored code P07C8 may be the only sign, especially if the fault is intermittent

Common causes, most likely first

  1. Damaged or disconnected wiring or connector at the intermediate shaft speed sensor B
  2. Open circuit in the signal or reference voltage wire between the sensor and the PCM
  3. Short to voltage on the signal circuit, often from chafed insulation
  4. Failed intermediate shaft speed sensor B
  5. Poor electrical connection at the PCM connector
  6. Internal PCM fault, though this is less common

How to diagnose and fix it

  1. Inspect the sensor and its connector for physical damage, corrosion, or loose pins
  2. Check the sensor's resistance and compare it to the manufacturer's specification
  3. Measure voltage on the signal circuit with the key on and engine off to verify reference voltage
  4. Perform a wiggle test on the harness while monitoring sensor voltage to find intermittent opens
  5. Check continuity and resistance of the signal and ground circuits between the sensor and PCM
  6. If wiring and sensor test good, substitute a known-good sensor to see if the code returns
  7. As a last resort, diagnose the PCM for internal faults after all other possibilities are ruled out

Don't overlook the harness before replacing the sensor

  • A common mistake is replacing the speed sensor without checking the harness, yet chafed or broken wires near the transmission often cause this code.
  • The intermediate shaft speed sensor B is sometimes confused with the output shaft speed sensor, so verify the correct component location using the service information.
  • Intermittent high-voltage codes can be set by a loose ground connection at the transmission or engine block, which affects the sensor's reference voltage.
  • After repairs, the code may not clear immediately because the PCM needs to see a clean signal over several drive cycles before turning off the light.
  • Some vehicles use a single sensor for both intermediate and output shaft speeds, so a fault in one circuit can affect multiple speed readings.

Can I keep driving with P07C8?

You can usually drive the vehicle with this code, but avoid aggressive acceleration or heavy towing because the transmission may shift erratically or enter limp mode. Have the fault diagnosed soon to prevent potential transmission damage.

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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