Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Code 31, Park/Neutral Switch Circuit - 3.8L: Notes
Park/neutral switch contacts are part of neutral start switch. Contacts close to ground in Park or Neutral and open in Drive. Code 31 will set if park/neutral signal circuit indicates an open for 3 consecutive starts or if conditions occur as follows with ignition on and engine off.
- Vehicle speed is zero MPH.
- Gear selector switch indicates a gear other than Park or Neutral.
- Gear selector status indicates an incorrect combination of LO and HI for more than 10 seconds.
Code 31 does not turn on SERVICE ENGINE SOON light.
- This tests for proper operation of gear selector switch.
- This tests for proper operation of gear selector switch.
- Tests for an open of grounded circuit.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.