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DTC codes / P09xx · Transmission / P0927

P0927Gear Shift Reverse Actuator Circuit High

P0927 means the transmission control module (TCM) has detected an abnormally high voltage on the electrical circuit that controls the reverse gear shift actuator, which is the solenoid or motor that engages reverse. The TCM monitors the actuator circuit and sets this code when the voltage exceeds the expected range, indicating an open circuit, a short to power, or a faulty actuator.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaTransmission

Symptoms you may notice

  • The reverse gear may fail to engage when selected, or engagement may be delayed or harsh.
  • The check engine light or transmission warning light illuminates on the dashboard.
  • The transmission may enter limp mode, limiting operation to a single gear or a reduced set of gears.
  • The driver may notice a burning smell or unusual noises from the transmission area if the actuator is stuck.
  • Often no symptoms besides the warning light, especially if the fault is intermittent.

Common causes, most likely first

  1. A faulty reverse gear shift actuator (solenoid or motor) with an open internal coil or high resistance.
  2. Damaged, corroded, or disconnected wiring or connector pins in the actuator circuit.
  3. A short to voltage in the harness between the TCM and the actuator.
  4. A failed transmission control module (TCM) driver circuit for the actuator.
  5. Poor ground connection for the actuator or TCM, causing reference voltage errors.
  6. Aftermarket electrical accessories improperly tapped into the actuator circuit.

How to diagnose and fix it

  1. Use a scan tool to read the freeze-frame data and verify the code is current, then clear it and test-drive to see if it returns.
  2. Visually inspect the actuator connector and wiring for corrosion, chafing, or loose pins, and repair as needed.
  3. Measure the resistance of the reverse gear shift actuator with a multimeter and compare to the manufacturer's specification; replace if out of range.
  4. Check for short to voltage on the signal circuit by backprobing the TCM connector with the actuator disconnected and the key on.
  5. Verify the actuator ground circuit with a voltage drop test under load, repairing any excessive resistance.
  6. If the circuit and actuator test good, substitute a known-good TCM or reprogram the existing module as a last step.
  7. After repairs, clear codes and perform a relearn or adaptation procedure if required by the manufacturer.

What the voltage reading really tells you

  • A high voltage code on an actuator circuit often results from a poor ground rather than a failed actuator, so always perform a voltage drop test on the ground side before condemning parts.
  • Intermittent P0927 can be caused by water intrusion into a connector that only acts up in wet weather, so inspect for green corrosion or missing weather seals.
  • The TCM may set this code if the actuator circuit is open, which can happen from a broken wire inside the harness loom where it flexes near the transmission mount.
  • Do not overlook aftermarket remote starters or alarm systems that tap into the reverse circuit; they can backfeed voltage and trigger this code.
  • A faulty transmission range sensor or manual lever position sensor can cause the TCM to command reverse when it shouldn't, leading to actuator circuit codes that mimic a wiring fault.

Can I keep driving with P0927?

If the transmission still engages reverse and drive normally, you can drive cautiously to a repair shop, but avoid relying on reverse gear in tight situations. If the vehicle is in limp mode or reverse is completely inoperative, stop driving and have it towed to prevent further 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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