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P codepowertrainMedium severity

P07BCTransmission Park Position Sensor/Switch "B" Circuit Performance High

The transmission control module has detected that the park position sensor/switch "B" signal is reading higher than its expected performance range, so the module cannot reliably verify whether the transmission is in Park.

Definition

On transmissions with electronic Park sensing — especially shift-by-wire systems — the control module monitors the park position sensor/switch "B" signal to confirm the parking pawl or park mechanism state. P07BC sets when the signal is electrically alive but stuck or biased high beyond the range that is plausible for the commanded gear state, so the module cannot trust the reported Park status. Symptoms include a "Shift to Park" message with the vehicle already in Park, a no-crank or no key-off/lock condition, a transmission warning light, and on some vehicles automatic application of the electric park brake as a failsafe.

Common causes

  • Failed or drifting park position sensor/switch "B"
  • Corroded, contaminated, or backed-out terminals at the shifter or transmission connector
  • Misadjusted, worn, or binding park mechanism or shifter detent preventing full switch actuation
  • Chafed harness wiring shorted to voltage or with added resistance
  • Water intrusion into the shifter assembly or sensor connector
  • Faulty transmission control module input circuit (rare)

Common misdiagnoses

  • Replacing the entire shifter assembly when the fault is a connector or terminal-tension problem
  • Replacing the transmission range sensor (PRNDL sensor) for a dedicated park-sensor code
  • Replacing the TCM or PCM before verifying the sensor circuit
  • Internal transmission repair for what is an external sensor/wiring fault
  • Battery replacement for the resulting no-crank complaint

Troubleshooting steps

  1. 1.Scan all modules

    Record codes from the TCM, BCM, and shifter module plus freeze frame, and note any companion codes for sensor "A" or the range sensor.

  2. 2.Watch live park-sensor data

    Monitor the park position sensor "B" state or voltage while cycling Park to Drive and back, confirming whether the value tracks or stays pegged high.

  3. 3.Wiggle-test the harness

    Flex the harness and connectors at the shifter and transmission while watching the signal for shifts, which isolates connection faults.

  4. 4.Inspect connectors

    Check for corrosion, water intrusion, spread terminals, or backed-out pins at the sensor/shifter connector, a very common root cause.

  5. 5.Verify the park mechanism

    Confirm the shift mechanism or park actuator travels fully into Park so the switch is actually being actuated to its end position.

  6. 6.Replace the sensor/switch

    With wiring and mechanism verified, replace the park position sensor or shifter sensor unit per the service procedure and confirm correct state reporting.

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