Powertrain Controls - ECM/PCM

Code 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 digits displayed represent decoder A, B, C and Parity inputs in sequence.

Code 31 will set 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 0.13 second for 3 consecutive start-ups.
^ The PRNDL status indicators (A, B, C, P) indicate an incorrect combination of LO and HI for more than 10.0 seconds.

TEST DESCRIPTION: Numbers below refer to circled numbers on the diagnostic chart.

1. This step checks for proper operation of the PRNDL.

2. This step checks for proper operation of the PRNDL.

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

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 - If connections and harness check OK, observe Tech 1 display 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." Moving the gear selector slowly through each gear position while monitoring the PRNDL switch with the Tech 1 may locate a faulty switch. This may help to isolate the location of the malfunction.