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.

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HOMESERVICE MANUALSCHEVROLET1992CHEVY VAN G20, 5.7 KREPAIR AND DIAGNOSIS (SINGLE PAGE)TRANSMISSIONAUTOMATIC TRANSDIAGNOSIS - A/TDIAGNOSTIC FLOW CHARTS (CARS)CODE 31, PARK/NEUTRAL SWITCH CIRCUIT - 3.8L PFI (VIN L)NOTES

1992 Chevrolet Chevy Van G20, 5.7 K

Code 31, Park/Neutral Switch Circuit - 3.8L PFI (VIN L): Notes

1992 Chevrolet Chevy Van G20, 5.7 KSECTION Notes

Fig 1: Code 31, Park/Neutral Switch Circuit Diagram (3.8L PFI - VIN L)

Courtesy of GENERAL MOTORS CORP.

PRNDL switch is mounted on transaxle assembly. Switch sends information relative to gear selector position to PCM. PRNDL assembly also contains neutral safety switch. PRNDL switch uses 4 discrete circuits to pull 4 PCCM voltages low in various combinations to indicate each gear range. Voltage level of each of the circuits is represented as LO being grounded and HI being open. The 4 digits displayed represent Code 31 sets under the following conditions:

Ignition is on and engine is off
Vehicle speed is 0 MPH
PRNDL indicates a gear other than Park or Neutral
All conditions met for 13 seconds for 3 consecutive starts.
PRNDL status indicators (A, B, C and P) indicate an incorrect combination of LO and HI for more than 10 seconds.
When a Code 31 is present, PCM assumes the D4 position until a correct combination is received by PCM. Some gear select positions may not be possible until fault is repaired.
NOTE: Test numbers refer to test numbers on diagnostic chart.
1. This test checks for proper operation of PRNDL.
2. This test checks for proper operation of PRNDL.
3. This test checks for open or grounded circuit.

RENDER: 1.0x

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.