P0929 Diagnostic Trouble Code: Gear Shift Lock Solenoid/Actuator “A” Control Circuit Range/Performance

Fault code P0929 is called “Gear Shift Lock Solenoid/Actuator “A” Control Circuit Range/Performance” but in different programs it may be called differently. This fault designation applies to all vehicles equipped with OBD-II.

Technical description and explained code P0929

This diagnostic trouble code (DTC) is a generic transmission code. Error P0929 is considered a generic code because it applies to all makes and models of vehicles. Although the specific repair steps may vary slightly depending on the model.

P0929 Diagnostic Trouble Code: Gear Shift Lock Solenoid/Actuator "A" Control Circuit Range/Performance

To prevent unintentional rollback, modern cars are equipped with what is called a shift lock solenoid.

When the computer determines that all conditions for safe shifting of the vehicle have been met. Your foot is on the brake pedal and the shift-lock button is pressed, the shift-lock solenoid is unlocked. The computer then allows the transmission to shift into gear.

When the control module (TCM) detects an operating range mismatch in the shift-lock solenoid/actuator “A” control circuit. Fault code P0929 will be written to memory, and an error message will appear on the control panel.

That is, the error indicates a discrepancy between the actual data and the reference data in the control circuit of this solenoid.

Symptoms of vehicle malfunctions

The main signal that an error P0929 has occurred is the Malfunction Indicator Lamp (MIL) is also known as the CheckEngine Light.

It can also be warning signs such as:

  1. The “Check engine” control lamp on the control panel will light up (the code will be stored as a fault).
  2. The transmission cannot shift out of parking mode.
  3. There may be no symptoms other than a stored fault code.

A stored fault code P0929 is considered serious because if it occurs, you will not be able to shift into gear and therefore not be able to drive. The conditions that have contributed to the stored code should be corrected as soon as possible.

Factors that can cause this error code

The error code P0929 can mean that one or more of the following problems have occurred:

  • The shift locking solenoid is defective.
  • Low level or contaminated transmission fluid.
  • Shorted or damaged wiring harness.
  • Faulty wiring harness connector.
  • Fuse or fusible link is blown.
  • Low battery voltage.
  • Defective brake light switch.
  • Transmission control module (TCM) may be defective.

How to fix or reset OBD-2 code P0929

Some suggested steps for troubleshooting and fix the error code P0929:

  1. Read all stored data and error codes with an OBD-II scanner.
  2. Clear the error codes from the computer memory.
  3. Test-drive the vehicle to see if error P0929 appears again.
  4. Visually inspect the appropriate wires and connectors for damage.
  5. Check the shift-lock solenoid.
  6. Test the brake light switch.
  7. Check the quality and level of the transmission fluid.
  8. Test the transmission control module (TCM).

Diagnose and repair of problems

The first thing to do when diagnosing code P0929 is to check the electrical part for damage. In today’s vehicles, electrical and electronic signals require good cabling for proper data transmission.

Any faults, such as breaks, disconnected connectors or corrosion, can interrupt signals, leading to transmission control failures. Next, check the battery, as some PCM and TCM modules are sensitive to low voltage.

If the battery is low, the system may detect this as a failure. Check that the battery is delivering a minimum of 12 volts and that the alternator is operating properly, a minimum of 13 volts at idle.

If no malfunction is detected, check the shift-lock solenoid. It usually fails due to moisture ingress and oxidation of the contacts.

The transmission control module (TCM) fails very rarely, so when diagnosing error P0929, it should be checked if all other checks have been done.

On which vehicles does this problem occur most frequently

Fault code P0929 can occur on different vehicles but there are statistics on which brands this occurs most often. Here is a list of some of them:

  • Audi
  • Ford (Fusion)
  • Land Rover (Range Rover)
  • Skoda (Octavia, Rapid)
  • Volkswagen

Fault code P0929 can sometimes be found with other errors. The most common are the following: P0928, P0930, P0931.


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