P0931 code definition
The P0931 trouble code detects an issue with the gear shift lock solenoid circuit.
What the P0931 code means
The P0931 code is a generic OBD-II trouble code that notes a voltage reading problem with the gear shift lock solenoid circuit. The gear shift lock solenoid is responsible for making sure that the automatic transmission is unable to move out of the Park position unless the brake pedal is deployed. When the system detects that the brake pedal has been pressed, the gear shift lock solenoid allows the shifter to move from Park into Drive or Reverse. If the powertrain control module (PCM) detects that the voltage reading from the gear shift lock solenoid circuit is abnormally high, then the P0931 code will be stored.
What causes the P0931 code?
A few different things can cause the P0931 trouble code to be triggered:
- Defective gear shift lock solenoid
- Defective brake light switch
- Low battery voltage
- In rare cases, a defective PCM
- Damaged electrical components in the circuit, such as wires and connectors
What are the symptoms of the P0931 code?
The P0931 trouble code will usually be accompanied by the Check Engine Light illuminating on the vehicle’s dashboard. The gear shifter will almost always be stuck in Park, so the car cannot be put in gear.
How does a mechanic diagnose the P0931 code?
The P0931 code will be diagnosed using a standard OBD-II trouble code scanner. A trained technician will observe the freeze frame data from the scanner to gather information about the code, and to see if any other trouble codes are present. If multiple different codes are detected, then they should be taken care of in the order that they appear in. The mechanic will then need to clear the trouble codes and restart the vehicle, to see if the P0931 code is still detected. If it is not, then it was either triggered erroneously, or represents an intermittent error.
If the code does remain following the reset, the mechanic will begin with a visual inspection of the system’s electrical components. Any loose or corroded connectors, or open or shorted wires will need to be replaced. The battery should then be checked to make sure that it is properly charged.
Next, the gear shift lock solenoid should be inspected, and tested for continuity. This is the most likely culprit of the P0931 code, but if the solenoid appears to be in working order, then the brake light switch will need to be checked.
After any replacement, the mechanic should pause the inspection and reset the trouble codes and restart the vehicle, to see if the code returns. By doing this, the technician will know as soon as the P0931 code has been resolved.
Common mistakes when diagnosing the P0931 code
The most commonly made mistake when diagnosing the P0931 code is the failure to properly follow the OBD-II trouble code diagnosis protocol. It’s very important that the protocol be followed, as it helps mechanics avoid erroneous repairs. For instance, it is common for the solenoid to be assumed defective, which risks overlooking damaged electrical components and replacing a functioning piece.
How serious is the P0931 code?
A car with the P0931 trouble code will probably not be drivable, because in most cases the vehicle will not be able to shift out of Park. The vehicle will likely require an inspection and repair before it can be driven.
What repairs can fix the P0931 code?
Common fixes for the P0931 trouble code are:
- Replacement of the gear shift lock solenoid
- Replacement of wires and connectors
- Replacement of the brake light switch
- Recharge or replacement of the battery
Additional comments for consideration regarding the P0931 code
The P0931 trouble code only applies to vehicles with automatic transmissions. If the car is stuck somewhere and needs to be moved, most transmissions have a fail-safe mechanism built into the shifter, which can be activated with a screwdriver.
Need help with a P0931 code?
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