Definition of Code P0931
Fault code P0931 detects a problem with the shift lock solenoid circuit.
What does code P0931 mean?
Code P0931 is a generic OBD-II fault code that indicates a voltage reading issue with the shift lock solenoid circuit. The shift lock solenoid is responsible for ensuring that the automatic transmission cannot shift out of the Park position unless the brake pedal is applied. When the system detects that the brake pedal has been pressed, the shift lock solenoid allows the gear lever to move from Park to Drive or Reverse. If the Powertrain Control Module (PCM) detects that the voltage reading from the shift lock solenoid circuit is abnormally high, code P0931 will be stored.
What causes code P0931?
Several different things can trigger fault code P0931:
Faulty shift lock solenoid
Faulty brake light switch
Low battery voltage
In rare cases, a faulty PCM
Damaged electrical components in the circuit, such as wires and connectors
What are the symptoms of code P0931?
Fault code P0931 will usually be accompanied by the Check Engine light illuminated on the vehicle’s dashboard. The gear lever will almost always be stuck in Park, so the car cannot be driven.
How does a mechanic diagnose code P0931?
Code P0931 will be diagnosed using a standard OBD-II fault code scanner. A qualified technician will observe the scanner’s freeze frame data to gather information about the code and see if other fault codes are present. If multiple different codes are detected, they must be addressed in the order they appear. The mechanic will then need to clear the fault codes and restart the vehicle to see if code P0931 is still detected. If not, it was triggered in error or represents an intermittent issue.
If the code persists after resetting, the mechanic will begin with a visual inspection of the electrical components in the system. Any loose or corroded connectors, or open or shorted wires will need to be replaced. The battery should then be checked to ensure it is properly charged.
Next, the shift lock solenoid must be inspected and tested for continuity. It is the most likely culprit for code P0931, but if the solenoid appears to be functioning, then the brake light switch will need to be checked.
After any replacement, the mechanic should pause the inspection, reset the fault codes, and restart the vehicle to see if the code returns. By doing this, the technician will know as soon as code P0931 has been resolved.
Common mistakes when diagnosing code P0931
The most frequent mistake made when diagnosing code P0931 is failing to properly follow the OBD-II fault code diagnostic protocol. It is very important to follow the protocol, as it helps mechanics avoid incorrect repairs. For example, it is common to assume the solenoid is faulty, which risks overlooking damaged electrical components and replacing a functional part.
How severe is code P0931?
A car with fault code P0931 will likely not be drivable, as in most cases, the vehicle will not be able to shift out of Park. The vehicle will probably need to be inspected and repaired before it can be driven.
What repairs can fix code P0931?
Common fixes for fault code P0931 are:
- Replacing the shift lock solenoid
- Replacing wires and connectors
- Replacing the brake light switch
- Recharging or replacing the battery