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.
Chart C1A - Park/Neutral Switch (Auto. Trans. Only)
The Park/Neutral switch contacts are a part of the neutral start switch and are closed to ground in Park or Neutral and open in Drive ranges. The ECM supplies ignition voltage through a current limiting resistor to circuit No. 434 and senses a closed switch when voltage on circuit No. 434 drops to less than one volt. The ECM uses the P/N signal as one of the inputs to control Idle Air Control (IAC) and VSS diagnostics.
- This test checks for a closed switch to ground in Park position. If using an ohmmeter, instead of a test light or "Scan" tester, the resistance will be low, indicating continuity to ground.
- This test checks for an open switch in Drive range.
- Ensure that "Scan" tester indicates Drive while wiggling shifter to test for a faulty or misadjusted switch.
NO RELATED
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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.