OBD-II trouble code
P0931: Gear Shift Lock Solenoid Control Circuit High
A high-voltage or open condition on the shift lock circuit. Worth knowing before you decide how urgent it is: the interlock is not a convenience feature but a legally required safety device, and a car that leaves Park without the brake has failed that requirement.
Quick facts
- System
- Powertrain
- Category
- Transmission / Shift Control
- Severity
- Medium severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $60 – $620
- DIY difficulty
- Intermediate DIY
What does P0931 mean?
P0931 is set when the module commanding the shift lock solenoid sees the circuit sitting higher than expected — the drive wire not pulling down when commanded, an open somewhere in the loop, or voltage arriving from somewhere it should not. Depending on how the vehicle's lock is arranged, the practical result is either a lever that stays locked in Park or a lever that is no longer locked at all.
That second outcome is the one worth taking seriously, and it is the reason this code exists rather than being left as a comfort feature nobody monitors. The brake-transmission shift interlock is a regulatory requirement on automatics in the United States and its equivalents apply across most other markets. The hazard it exists to prevent is specific and documented: a vehicle parked with the engine running, a lever knocked or pulled by someone reaching across or by a child left in the cabin, and a car that moves off with nobody controlling it. A P0931 that has left the lock disengaged means that protection is gone even though the vehicle drives perfectly and shows no other sign of trouble. That also gives it a consequence no other code in this range has: it is a safety-related defect that a roadworthiness or periodic inspection can legitimately fail the vehicle on, and it will not be discovered by a road test because there is nothing to feel.
The modern complication is keyless vehicles. On a car with push-button start and electronic Park selection, the interlock logic has been folded into the shutdown strategy — the module wants to see Park confirmed before it will allow the vehicle to power down, and many designs will engage Park automatically if the driver opens the door and walks away without doing so. When the interlock circuit faults on one of these, the presenting complaint is frequently nothing to do with the gear lever at all. The car refuses to shut off, or it warns about Park every time the door opens, or it re-engages Park at a moment the driver did not expect. Owners describe this as an ignition fault or a door sensor fault, and the shift lock circuit is not where anyone looks first.
Electrically, a high circuit on this component is far more often an open than a short to power. The three usual candidates are a disconnected or partially backed-out connector at the base of the selector assembly, a broken solenoid winding, and a corroded ground. A solenoid that has failed open reads high because there is nothing at the other end of the wire to pull it down, which is indistinguishable from an unplugged connector until you go and look.
Common causes
- Open circuit in the shift lock solenoid drive or ground wire
- Solenoid winding failed open after long service
- Connector at the base of the selector assembly unplugged or with a backed-out pin
- Corroded ground connection for the interlock circuit
- Short to battery voltage on the drive wire
- Failed low-side driver inside the control module
- Broken solder joint or track inside the selector assembly
- Harness damage from console removal for stereo, alarm or trim work
- Interlock circuit disturbed by an aftermarket remote start installation
- Wiring damaged by seat rail movement where the loom runs alongside the console
Symptoms
- Lever able to leave Park without the brake pedal pressed
- Lever locked in Park and refusing to release at all
- Warning lamp with a shift interlock or transmission message
- Keyless vehicle refusing to power down or warning about Park at every door opening
- Automatic Park engagement occurring at unexpected moments
- No audible click from the console when the brake is pressed
- Fault present from the first start of the day and never clearing
- Symptom appearing immediately after console or accessory work
- Vehicle otherwise driving and shifting entirely normally
- Fault reappearing after a clear without any driving in between
Diagnostic steps
- 1.Establish which way the fault has failed: try moving the lever out of Park without the brake pressed, because a lock that no longer holds is the safety-relevant version.
- 2.On a keyless vehicle, check whether the complaint is really about shutdown or automatic Park engagement rather than the lever, since that is how this fault usually presents there.
- 3.Read live data for the commanded state of the solenoid and compare it against what the lever actually does.
- 4.Unplug the solenoid and check whether the reading changes — if it does not, the open is upstream of the connector.
- 5.Measure solenoid coil resistance; an open winding and an unplugged connector produce identical circuit readings.
- 6.Perform a voltage drop test on the ground leg, as a corroded ground raises the circuit just as an open drive wire does.
- 7.Back-probe the connector at the selector assembly rather than testing at the module, so a backed-out pin is not missed.
- 8.Inspect the loom where it runs beside the seat rail and under the console for a break caused by movement or by previous trim removal.
- 9.Check for any aftermarket wiring spliced into the interlock circuit, which is a common tapping point for remote start systems.
- 10.Confirm the repair by verifying the lock actually holds the lever in Park with the brake released, not merely that the code has cleared.
Repair cost
$60 – $620
Diagnosis is $60 to $180. Repairing an open or corroded circuit — a broken wire, a bad ground, a backed-out pin — is $80 to $260 and is the most common outcome. A shift lock solenoid supplied separately is $110 to $400 fitted; on vehicles where the manufacturer only supplies the complete selector assembly, $260 to $620. On keyless vehicles where the electronic selector module is integrated, expect the upper half of that range. If the lock has failed disengaged, treat the repair as safety work rather than deferrable comfort work.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with shift interlock (shift lock) solenoid replacement preselected. Adjust labor rate and vehicle category to fit your situation.
DIY vs shop
This is an intermediate DIY job. It usually involves diagnostic steps, specialty parts, and some careful work in tight spaces. If you have the tools and a service manual or trustworthy video for your specific vehicle, it is achievable in a weekend. Otherwise, a competent independent shop will be faster.