Gear Shift Lock Solenoid Control Circuit Range/Performance
Diagnostic trouble code P0929 indicates that the powertrain control module (PCM) or transmission control module (TCM) has detected an out-of-range or performance issue in the gear shift lock solenoid control circuit. This means the voltage or resistance in the circuit is not within the expected parameters, potentially preventing the shift interlock system from operating correctly.
While not immediately dangerous to the engine, this code can leave you stranded if the vehicle becomes stuck in Park. It should be diagnosed and repaired soon to ensure reliable vehicle operation.
Common symptoms
- Illuminated Check Engine Light
- Inability to shift out of Park
- Gear shift lever moves without pressing the brake pedal (rare)
- Need to use the manual shift lock override to move the shifter
- Erratic operation of the shift interlock system
Likely causes
- Faulty gear shift lock solenoid
- Damaged, corroded, or loose wiring and connectors in the shift lock solenoid circuit
- Faulty brake light switch
- Blown fuse in the shift interlock circuit
- Spilled liquids on the center console damaging the shifter assembly
- Faulty Transmission Control Module (TCM) or Powertrain Control Module (PCM)
What to check before replacing parts
Check the relevant fuses for the shift interlock and brake light circuits.
Look for: A blown fuse indicates a short circuit or overload that needs to be addressed before replacing the fuse.
Verify the operation of the brake light switch.
Look for: Ensure the brake lights illuminate when the pedal is pressed; if they do not, the switch or its circuit may be faulty, preventing the shift lock from releasing.
Visually inspect the wiring and connectors at the gear shift lock solenoid.
Look for: Look for frayed wires, corrosion, loose connections, or signs of liquid intrusion (like spilled coffee) in the center console area.
Test the gear shift lock solenoid for proper resistance using a digital multimeter.
Look for: Compare the measured resistance to the manufacturer's specifications; an open or shorted reading indicates a failed solenoid.
Check for voltage and ground at the shift lock solenoid connector while pressing the brake pedal.
Look for: If battery voltage and a good ground are present when the brake is pressed but the solenoid doesn't actuate, the solenoid is defective. If voltage or ground is missing, trace the circuit back to find the open or short.
This page explains the generic P0929 definition and is general reference information, not a diagnosis for your specific vehicle. Actual causes, severity, and repairs vary by make, model, engine, and mileage — always confirm with a scan tool and a qualified technician before replacing parts.
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