P0931: Gear Shift Lock Solenoid/Actuator Control Circuit “A” High

The P0931 trouble code is an OBD-II diagnostic trouble code related to the gear shift lock solenoid or actuator control circuit.

P0931 – Gear Shift Lock Solenoid/Actuator Control Circuit “A” High

This code means that the transmission control system has detected higher-than-expected voltage or an abnormal electrical condition in the “A” gear shift lock solenoid/actuator control circuit.

The gear shift lock system is different from the transmission's normal shift solenoids. Its primary purpose is to prevent the transmission selector from being moved out of Park under certain conditions, most commonly until the brake pedal is pressed.

A fault in this system can cause problems with moving the gear selector between positions, particularly when attempting to move the selector out of Park (P).

Possible causes include:

• Faulty shift lock solenoid

• Faulty shift lock actuator

• Short to battery voltage

• Damaged wiring

• Corroded connector

• Loose electrical terminal

• Incorrect power supply

• Faulty brake pedal switch

• Damaged shift-lock mechanism

• Internal selector mechanism problem

• Body control module (BCM) fault

• Transmission control module fault

The exact system architecture varies between vehicles. On some vehicles, the shift lock function is controlled primarily by the BCM, while on others it may involve the TCM, PCM or another control module.

What Does P0931 Mean?

P0931 – Gear Shift Lock Solenoid/Actuator Control Circuit “A” High

Modern automatic vehicles commonly use an electronic shift lock system.

Its basic purpose is to prevent accidental movement of the gear selector from Park unless the required conditions are met.

A simplified system works like this:

Brake pedal → Brake switch → Control module → Shift lock solenoid → Gear selector

When the driver presses the brake pedal, the control system recognizes the brake input and allows the shift lock mechanism to release.

If the control module detects an abnormal voltage condition in the “A” shift lock solenoid/actuator circuit, it may store P0931.

What Is a Gear Shift Lock Solenoid?

The gear shift lock solenoid is an electrically controlled device that helps prevent the gear selector from being moved from Park when the required release conditions have not been met.

It is commonly located in or around the:

• Gear selector assembly

• Center console

• Shift lever mechanism

• Electronic shifter assembly

When the required conditions are satisfied, the solenoid releases a mechanical lock.

Depending on the vehicle, the system may also incorporate:

• Brake pedal switch

• Shift position sensor

• Control module

• Selector position sensor

• Wiring harness

• Manual shift-lock release mechanism

What Does “Circuit High” Mean?

The “High” in P0931 refers to the electrical circuit.

It does not mean:

• The vehicle is in a high gear

• Transmission fluid pressure is too high

• Engine RPM is too high

• The shift lock is physically stuck in the “high” position

The control module has detected that the electrical voltage or signal in the “A” circuit is higher than the expected value.

A possible example is:

Control wire shorted to battery voltage → Excessive circuit voltage → P0931

The shift lock solenoid itself may still be mechanically functional.

Symptoms of P0931

The most noticeable symptom is often related to the gear selector.

Possible symptoms include:

• Check Engine Light

• Transmission warning light

• Gear selector stuck in Park

• Difficulty moving the selector out of Park

• Shift lock not releasing

• Shift lock releasing at the wrong time

• Intermittent selector operation

• Brake lights not operating correctly

• Shift-lock warning message

• Electrical warning messages

In some vehicles, the selector may continue working normally while the fault code is stored.

Common Causes of P0931

Faulty gear shift lock solenoid

The solenoid can develop an internal electrical fault.

Possible problems include:

• Internal short

• Open winding

• Excessive resistance

• Mechanical sticking

• Wear

• Heat damage

Short to battery voltage

This is an important possibility for a circuit-high code.

If the control wire becomes connected to a power supply, the control module may detect excessive voltage.

Damaged wiring

The wiring around the center console and gear selector can be damaged by:

• Movement

• Chafing

• Pinching

• Previous repairs

• Liquid spills

• Heat

• Physical damage

Corroded connector

Corrosion can alter the electrical characteristics of the circuit and create an abnormal signal.

Loose terminal

A loose terminal may prevent the control module from controlling the solenoid correctly.

Incorrect power supply

An electrical supply problem can cause the shift lock circuit to operate outside its expected parameters.

Faulty brake pedal switch

The brake switch is an important part of the shift-lock system.

If the vehicle does not correctly recognize that the brake pedal has been pressed, the shift lock may not release.

However, a brake switch problem does not automatically mean that P0931 is caused by the switch itself. The specific circuit should be tested.

Damaged shift-lock mechanism

The electrical system may be working correctly while the mechanical locking mechanism is sticking or damaged.

Body control module problem

On many modern vehicles, the shift lock is controlled by the BCM or another body electronics module.

A BCM fault can therefore affect shift-lock operation.

Transmission control module problem

Depending on the vehicle, the TCM may be involved in the shift-lock system.

A TCM fault is possible but should generally be considered only after the circuit and related components have been tested.

Can a Bad Brake Switch Cause P0931?

A faulty brake pedal switch can cause shift-lock problems, but it is not automatically the cause of a circuit-high P0931.

The brake switch tells the vehicle that the brake pedal has been pressed.

If the switch fails, you may notice:

• Brake lights not working

• Brake lights staying on

• Gear selector not releasing from Park

• Cruise-control problems

• Brake-related warning messages

The brake switch should be checked if the shift lock does not release, especially if the brake lights are also malfunctioning.

Can a Dead Battery Cause P0931?

A weak battery or unstable electrical supply can cause various control-module faults.

However, a battery problem should not automatically be considered the cause of P0931.

Check:

• Battery voltage

• Charging voltage

• Battery terminals

• Ground connections

If several unrelated electrical fault codes appeared at the same time, power-supply problems become more relevant.

Is P0931 Related to the Transmission?

It can be related to the transmission control system, but it is primarily a gear-selector safety-lock circuit fault.

This distinction is important.

The gear shift lock prevents unintended movement of the selector from Park. It is not the same component as a normal transmission shift solenoid that controls hydraulic pressure and gear changes inside the transmission.

Therefore, P0931 does not automatically indicate internal transmission damage.

P0931 vs. P0930

P0930 – Gear Shift Lock Solenoid/Actuator Control Circuit “A”

This is a general fault involving the “A” shift lock solenoid/actuator circuit.

P0931 – Gear Shift Lock Solenoid/Actuator Control Circuit “A” High

This specifically indicates that the circuit voltage or signal is higher than expected.

P0931 vs. P0932

These codes concern different systems.

P0931 concerns the gear shift lock solenoid/actuator control circuit.

P0932 concerns the hydraulic pressure sensor circuit.

P0931 is therefore primarily associated with the electronic shift-lock system, while P0932 relates to transmission hydraulic pressure monitoring.

P0931 vs. P0933

P0931 is a shift-lock actuator circuit-high code.

P0933 is a hydraulic pressure sensor range/performance code.

The two codes can both be associated with transmission-related systems, but they monitor completely different components.

How Serious Is P0931?

P0931 is usually more of a drivability and safety-related electrical problem than an indication of major internal transmission damage.

However, it can become inconvenient or potentially unsafe if the shift selector cannot operate correctly.

The problem is particularly important if:

• The selector is stuck in Park

• The selector can move without the required brake input

• The brake lights are not working

• The shift lock behaves intermittently

If the vehicle cannot be safely shifted into the required gear, it should be inspected rather than repeatedly forcing the selector.

Can You Drive With P0931?

If the gear selector operates normally and the vehicle can safely be shifted between positions, it may be possible to drive the vehicle to a repair facility.

However, do not force a selector that is physically locked.

If the shift-lock system is malfunctioning, the vehicle may become difficult to move or there may be a safety concern if the interlock does not operate as intended.

Pay particular attention to whether the brake lights work correctly.

How to Diagnose P0931

Because P0931 identifies a circuit-high condition, electrical testing is essential.

1. Scan the vehicle

Use a diagnostic scanner capable of accessing the relevant control modules.

Check:

• BCM

• TCM

• PCM

• Selector module

• Other body-control systems

Record all stored and pending codes.

Other codes can provide important clues.

2. Check freeze-frame data

If available, review the conditions under which P0931 was stored.

Check:

• Battery voltage

• Brake pedal status

• Selector position

• Vehicle speed

• Ignition status

3. Check brake light operation

Press the brake pedal and verify that the brake lights operate correctly.

If the brake lights do not work, investigate the brake switch and its circuit before moving on.

4. Monitor brake pedal data

Use the scan tool to determine whether the control module recognizes the brake pedal being pressed.

You should see the brake switch status change when the pedal is operated.

5. Check shift-lock operation

Determine exactly what the selector is doing.

For example:

• Completely stuck in Park

• Releases intermittently

• Releases without brake input

• Operates normally but stores the code

This information can significantly narrow the diagnosis.

6. Inspect the shift-lock solenoid

Inspect the solenoid and its connector for:

• Damage

• Corrosion

• Loose terminals

• Bent pins

• Moisture

• Signs of overheating

7. Inspect the wiring

Look for:

• Shorted wires

• Damaged insulation

• Chafing

• Pinched wiring

• Broken conductors

• Liquid damage

• Previous repairs

Pay particular attention to wiring beneath or around the center console.

8. Check for unwanted voltage

Because P0931 is a circuit-high code, test the control circuit for unwanted voltage according to the manufacturer's diagnostic procedure.

A control wire that is shorted to battery voltage can produce P0931.

9. Test the solenoid resistance

If specifications are available, measure the resistance of the shift-lock solenoid.

Compare the result with manufacturer specifications.

An abnormal reading may indicate an internal solenoid problem.

10. Check power and ground

Verify that the shift-lock system receives the correct power and ground.

Check for:

• Voltage drop

• High resistance

• Poor ground

• Loose terminals

11. Test circuit continuity

Check the wiring between the shift-lock solenoid and the appropriate control module.

Test for:

• Open circuit

• Short to ground

• Short to voltage

• Excessive resistance

12. Perform an actuator test

If the diagnostic scanner supports active testing, command the shift-lock solenoid.

Observe whether it responds correctly.

13. Inspect the mechanical selector

If the electrical circuit works correctly, inspect the physical mechanism.

Look for:

• Mechanical obstruction

• Broken locking mechanism

• Foreign objects

• Sticking components

• Physical damage

14. Check the control module

If the wiring, solenoid, brake switch and mechanical components are functioning correctly, further testing of the BCM, TCM or selector control module may be necessary.

Why P0931 Can Be Misdiagnosed

A common mistake is assuming that P0931 means the transmission has a serious internal problem.

It does not.

The code specifically concerns the gear shift lock solenoid/actuator control circuit.

Another common mistake is replacing the shift-lock solenoid without checking for a short to voltage.

For example:

Damaged wire → Short to battery voltage → Circuit voltage too high → P0931

In this situation, replacing the solenoid would not solve the underlying problem.

Another mistake is ignoring the brake switch.

If the brake switch is malfunctioning, the shift-lock system may not receive the correct brake-pedal information.

P0931 and a Selector Stuck in Park

One of the most noticeable symptoms can be a selector that refuses to move out of Park.

The system generally requires a valid brake-pedal input before releasing the lock.

If the selector is stuck, check:

1. Brake lights

2. Brake pedal switch

3. Shift-lock fuse

4. Shift-lock solenoid

5. Solenoid wiring

6. Connector condition

7. Selector mechanism

8. Control-module data

Many vehicles also have a manual shift-lock release that can temporarily release the selector.

This should be used according to the vehicle manufacturer's instructions rather than as a permanent repair.

P0931 and Brake Lights

If P0931 occurs together with brake-light problems, the brake switch and its wiring deserve particular attention.

The shift-lock system and brake-light system can share information from the brake pedal switch.

A failed switch can therefore produce several symptoms at the same time.

P0931 After Center Console or Gear Selector Repair

If P0931 appears after work around the center console, inspect the area carefully.

Possible causes include:

• Pinched wiring

• Disconnected connector

• Partially inserted connector

• Damaged terminal

• Wiring trapped under the console

• Liquid contamination

This is particularly important when the fault appeared immediately after interior or selector-related work.

Can P0931 Damage the Transmission?

P0931 does not normally indicate a condition that directly damages internal transmission components.

The shift-lock mechanism is primarily a safety and selector-control system.

However, repeatedly forcing a stuck gear selector can damage the selector mechanism or surrounding components.

If the selector is locked, diagnose the electrical and mechanical cause instead of forcing it.

Common Diagnostic Mistakes With P0931

Common mistakes include:

• Replacing the solenoid without testing the circuit

• Ignoring the brake switch

• Assuming “High” means high transmission pressure

• Assuming the transmission needs replacement

• Ignoring wiring around the center console

• Failing to check the relevant fuse

• Replacing a control module before testing the circuit

The “High” designation should always be interpreted as an electrical circuit condition.

What Is the Correct Repair for P0931?

The correct repair depends on the confirmed cause.

Possible repairs include:

• Replacing the shift-lock solenoid

• Replacing the shift-lock actuator

• Repairing a shorted wire

• Repairing damaged wiring

• Replacing damaged connector terminals

• Repairing corroded connectors

• Replacing a faulty brake pedal switch

• Repairing the shift-lock mechanism

• Replacing a damaged fuse or correcting the underlying electrical problem

• Repairing selector wiring

• Repairing the BCM or selector control system where necessary

• Updating control-module software where applicable

• Replacing a control module only after it has been conclusively diagnosed as faulty

After the repair, clear the code and verify that:

• The brake lights operate correctly

• The selector remains locked when the required conditions are not met

• The selector releases correctly when the brake pedal is pressed

• The vehicle recognizes the correct selector position

• P0931 does not return

Final Thoughts on P0931

P0931 – Gear Shift Lock Solenoid/Actuator Control Circuit “A” High indicates that the vehicle's control system has detected higher-than-expected voltage or an abnormal electrical condition in the “A” gear shift lock solenoid/actuator circuit.

This system is primarily responsible for preventing unintended movement of the gear selector from Park. It should not be confused with the conventional transmission shift solenoids that control gear changes internally.

Possible causes include a faulty shift-lock solenoid, short to battery voltage, damaged wiring, corroded connectors, loose terminals, brake switch problems, selector mechanism faults or control-module issues.

The most effective diagnosis is to check the brake-pedal input, inspect the shift-lock solenoid and wiring, test the circuit for unwanted voltage, verify power and ground, and inspect the mechanical selector mechanism.

P0931 does not automatically mean that the transmission is damaged or needs to be replaced. In many cases, the fault can be traced to the shift-lock electrical circuit, brake switch, connector or wiring rather than the transmission itself.