Code E031, Park/Neutral Switch Circuit
The Park/Neutral (P/N) switch contacts are part of the neutral start switch and are closed to ground in Park or Neutral, and open in Drive. The ECM supplies ignition voltage through a current limiting resistor to circuit No. 434 and senses a closed switch when the voltage on circuit No. 434 drops to less than one volt. The ECM uses the P/N signal as one of the inputs to determine control of idle air control, EGR and VSS.
Code 31 will set under the following conditions:
- If circuit No. 434 indicates P/N (grounded) while in Drive range and 4th gear TCC engaged, EGR would be inoperative, resulting in possible detonation.
- If circuit No. 434 indicates Drive (open) at start up, a drop in idle may exist when gear selector is moved into Drive range.
- If transaxle 4th gear switch has an intermittent open, ECM thinks vehicle is in 4th gear and will set Code E031.
Test Number 1) Checks for a switch closed to ground in Park position.
Test Number 2) Checks for an open switch in Drive range.
Test Number 3) Ensure that on-board diagnostics EI74 indicates Drive (HI), even while wiggling shifter. This will test for an intermittent or misadjusted switch in Drive or Overdrive range.