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 Diagnosis (Auto Trans.)
The park/neutral switch is closed to ground in park or neutral, and open in drive ranges. The ECM supplies 12 volts through an internal resistor to circuit No. 434 and senses that switch is closed when voltage at terminal B10 drops to less than one volt.
- Checks for a closed switch to ground in park position. Different makes of "SCAN" tester will read P/N differently. Refer to "SCAN" tester operations manual for type of display used.
- Checks for an open switch in drive range.
- Be sure "SCAN" tester indicates drive, even while wiggling shifter to test for an intermittent or misadjusted switch in drive range.
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.