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DTC codes / P07xx · Transmission / P07B4

P07B4Transmission Park Position Sensor/Switch A Circuit High

P07B4 means the transmission control module (TCM) has detected an abnormally high voltage on the signal circuit for the transmission park position sensor or switch, typically indicating an open circuit, a short to voltage, or a faulty sensor. The TCM expects a specific voltage range when the shifter is in Park, and a reading above that range sets this code.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaTransmission

Symptoms you may notice

  • The check engine light or transmission warning light is illuminated, often with no other noticeable symptoms.
  • The vehicle may fail to recognize that the transmission is in Park, preventing the engine from starting or the key from being removed.
  • The gear position indicator on the dashboard may not show 'P' or may flash erratically.
  • The transmission may not engage Park properly, allowing the vehicle to roll when parked.
  • In some cases, the vehicle may not shift out of Park or may default to a limp mode.

Common causes, most likely first

  1. A faulty transmission park position sensor or switch (internal failure or contamination).
  2. An open circuit in the signal wire between the sensor and the TCM (broken wire, corroded connector, or loose pin).
  3. A short to voltage on the signal circuit, often from chafed wiring near the transmission or shifter assembly.
  4. Poor electrical connection at the sensor or TCM connector (corrosion, water intrusion, or terminal tension loss).
  5. A failed TCM or a software issue in the TCM (less common but possible).
  6. Mechanical damage to the sensor or its mounting inside the transmission, such as from debris or a worn park pawl mechanism.

How to diagnose and fix it

  1. Verify the code with a scan tool and check for any related codes in the TCM and other modules.
  2. Inspect the wiring harness and connectors at the transmission park position sensor for damage, corrosion, or loose pins.
  3. Measure the sensor's signal voltage with a multimeter and compare it to the manufacturer's specification while moving the shifter through all positions.
  4. Check for continuity and shorts to voltage on the signal circuit between the sensor and the TCM.
  5. If the wiring and connections are good, test the sensor itself according to the service manual; replace it if it fails the resistance or voltage test.
  6. Clear the code and perform a road test to confirm the repair, ensuring the park position is correctly recognized.
  7. If the code persists after sensor and wiring repairs, diagnose the TCM and consider reprogramming or replacement as a last resort.

Park sensor faults that mimic wiring issues

  • A common misdiagnosis is replacing the transmission park position sensor when the real problem is a chafed wire in the harness near the shifter or transmission, so always inspect the wiring first.
  • The sensor may test fine when cold but fail intermittently when hot, so a wiggle test and a live data scan while moving the shifter can reveal an intermittent fault that a static multimeter test misses.
  • On some vehicles, a weak or failing battery can cause voltage spikes that set this code, so check the charging system before condemning the sensor.
  • The park position signal is often shared with the body control module for key removal and start authorization, so a fault here can cause starting or key-off issues that seem unrelated to the transmission.
  • After replacing the sensor, some vehicles require a relearn or calibration procedure with a scan tool to teach the TCM the new sensor's voltage range, otherwise the code may return.

Can I keep driving with P07B4?

If the vehicle starts and drives normally, you can drive it to a repair shop, but avoid parking on an incline because the transmission may not securely engage Park. If the vehicle will not start or shift out of Park, do not force it; have it towed to prevent damage or a rollaway hazard.

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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