DTC 31

Code 31 Chart:

Code 31 Wiring Diagram:

CIRCUIT DESCRIPTION:

The park/neutral switch contacts are a part of the neutral start switch. They are open in drive and closed in Park or Neutral.


The ECM supplies ignition voltage through a current limiting resistor to CKT 434 and senses a closed switch when the voltage on CKT 434 drops to less than one volt. The ECM uses the P/N signal as one of the inputs to control, idle Speed (IAC), spark advance, and Vehicle Speed Sensor Diagnostics (VSS)


Code 31 will set if:

^ CKT 434 indicates an open for 3 consecutive starts.
^ No Code 38.
^ TCC is locked (4 speed only).
^ Transmission in high gear.
^ VSS greater than 45 mph and TPS less than 15% (0.94 volts).
^ Above conditions met for for 12 seconds.


NOTE: Because of all the possible color code combinations used on electrical wiring diagrams, always refer to ECM CONNECTOR IDENTIFICATION under ELECTRICAL AND ELECTRONIC WIRING DIAGRAMS for correct color code identification of circuit.


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

1. Checks for a closed switch to ground in park position. Different makes of "Scan" tools will read P/N differently.



2. Checks for an open switch in drive range.


3. Be sure "Scan" indicates drive, even while wiggling shifter, to test for an intermittent or mis-adjusted switch in drive or overdrive range.