DTC 31

DTC 31 - Park/Neutral Position (PNP) Input Circuit:

Electronic PRNDL Decoder Wiring Circuit:

Circuit Description:

The Park/Neutral Position (PNP) input is grounded by the electronic transmission range (PRNDL) decoder in park or neutral and open in drive ranges.

The ECM supplies ignition voltage through a current limiting resistor to CKT 434 and senses a grounded input when the voltage on CKT 434 drops to less than one volt.

The ECM uses the PNP signal as one of the inputs to control:
^ Idle speed (IAC).
^ Vehicle Speed Sensor (VSS) diagnostics.
^ Spark advance.

DTC 31 will set if:
^ CKT 434 indicates an open for 3 consecutive starts.
OR
^ CKT 434 indicates a ground.
^ No DTC 38.
^ Transmission is in high gear.
^ VSS greater than 45 mph and throttle angle less than 20% (.94 volt).
^ Above conditions are met for 12 seconds.

DTC 31 does not illuminate the MIL (Service Engine Soon).

Test Description: Number(s) below refer to circled
number(s) on the diagnostic chart.
1. Checks for a grounded PNP input in park position.
2. Checks for a faulty ECM.
3. Checks for an ungrounded PNP input in drive range. Be sure Tech 1 display indicates drive, even while wiggling shifter. If it doesn't, check for a misadjusted transmission range switch or an intermittent.