Gear Shift Lock Solenoid Control Circuit High
Diagnostic trouble code P0931 indicates that the transmission control module has detected a high electrical voltage in the gear shift lock solenoid control circuit. This circuit is responsible for operating the interlock mechanism that prevents the transmission from being shifted out of Park unless the brake pedal is applied.
While this code does not typically indicate internal transmission damage, it can leave you stranded because the vehicle may be locked in Park. It requires prompt attention to restore normal shifting operation.
Common symptoms
- Gear shifter is stuck in the Park position
- Check Engine Light is illuminated
- Need to use the manual shift lock override to move the shifter
- Inability to remove the ignition key (on some models)
- Brake lights may not operate correctly (if the brake switch is the root cause)
Likely causes
- Short to voltage in the shift lock solenoid wiring harness
- Faulty gear shift lock solenoid
- Defective brake light switch
- Corroded or damaged electrical connectors in the shift lock circuit
- Spilled liquid on the center console damaging the shifter assembly
- Faulty Transmission Control Module (TCM) or Body Control Module (BCM) (rare)
What to check before replacing parts
Verify brake light operation when pressing the brake pedal
Look for: If the brake lights do not illuminate, the brake switch or its circuit is likely faulty, preventing the shift lock from releasing.
Visually inspect the wiring and connectors around the shifter assembly
Look for: Look for frayed wires, pinched harnesses, or signs of liquid intrusion (like spilled coffee) that could cause a short to voltage.
Test the gear shift lock solenoid for proper resistance using a multimeter
Look for: Compare the measured resistance to the manufacturer's specifications; an open or internally shorted solenoid requires replacement.
Check the shift lock solenoid control circuit for a short to voltage
Look for: With the solenoid disconnected, probe the control wire; if battery voltage is present when it shouldn't be, there is a short to power in the harness.
Scan for related BCM or ABS codes
Look for: Additional codes related to the brake switch or body control module can pinpoint the source of the incorrect voltage being sent to the shift lock circuit.
This page explains the generic P0931 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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