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