Powertrain Controls - ECM/PCM

DTC 31 PRNDL Error:

Transmission Range Switch (PRNDL) Schematic:

CIRCUIT DESCRIPTION
The transmission range switch is mounted on the transaxle assembly. It is a multi-signal switch sending information indicating gear selector position to the Powertrain Control Module (PCM). The transmission range 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 LOW = Grounded, HIGH = open circuit. The 4 states displayed represent decoder P, A, B and C inputs in sequence.

DIAGNOSTIC TROUBLE CODE (DTC) 31 WILL SET WHEN
^ PCM recognizes an invalid PRNDL parameter.
^ Vehicle speed Sensor (VSS) is greater than 5 mph.
^ Above conditions are met for 5 seconds or more.

ACTION TAKEN (PCM WILL DEFAULT TO)
Cooling fan will enable.

DTC CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.

1. This checks for proper operation of the transmission range switch.
2. This checks for proper operation of the transmission range switch.
3. This test checks for an open or grounded circuit. When a fault is present, the PCM assumes the D3 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
Poor connection or damaged harness
Inspect PCM harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, 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 "LOW" to "HIGH" or "HIGH" to "LOW." Moving the gear selector slowly through each gear position while monitoring the PRNDL status with the Tech 1 may locate a faulty switch. This may help to isolate the location of the malfunction.