DTC 31

PRNDL Switch Circuit:

Circuit Description:
The PRNDL switch is mounted on the transaxle assembly. It is a multi-signal switch sending information relative to gear selector position to the PCM. The PRNDL assembly also contains the neutral safety (start) switch. The PRNDL switch uses 4 discrete circuits to pull 4 PCM voltages low in various combinations to indicate each gear range. The voltage level of each of the circuits is represented as LO = grounded, HI = open circuit. The 4 states displayed represent decoder Parity, A, B, and C inputs respectively.

Code 31 sets when:

^ Ignition is "ON" and engine is "OFF."
^ Vehicle speed is 0 mph.
^ PRNDL indicates a gear other than Park or Neutral (P/N).
^ All conditions met for .13 seconds for 3 consecutive start-ups.

OR

^ The PRNDL status indicators (P,A,B,C) indicate an incorrect combination of LO and HI for more than 10 seconds.

Code 31 does not illuminate the "Service Engine Soon" light.

Code 31 Diagnostic Chart:

Test Description:
Number(s) below refer to circled number(s) on the diagnostic chart.

1. This steps check for proper operation of the PRNDL.

2. This steps check for proper operation of the PRNDL.

3. This test checks for an open or grounded circuit.

When a Code 31 is present, the PCM assumes the D4 position until a correct combination is received by the PCM. Therefore, some gear select positions may not be possible until the fault is repaired.


Diagnostic Aids:
An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation.

Check for:

^ Poor Connection or Damaged Harness - Inspect PCM harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection and damaged harness.

^ Intermittent Test - Monitor a Tech 1 while moving related connectors and wiring harness. If the failure is induced, the "Scan" data will change from LO to HI or HI to LO.

This may help to isolate the location of the malfunction.