Code 31, Park/Neutral Switch CKT
Park/neutral switch contacts are part of neutral start switch. Contacts close to ground in Park or Neutral and open in Drive. Code 31 will set if park/neutral signal circuit indicates an open for 3-4 consecutive starts or if conditions occur as follows:
- Code 38 does not exist.
- Circuit No. 434 indicates ground.
- Transmission is in high gear.
- TCC is locked (4T60 transaxle).
- TPS is less than 15 percent (.94 volt) and vehicle speed is greater than 45 MPH (3T40 transaxle).
- All above conditions have been met for at least 12 seconds.
NOTE:
Test numbers refer to numbers on diagnostic chart.
- This tests for a closed switch to ground in Park.
- This tests for an ungrounded Park/Neutral input in Drive. Be sure TECH 1 display reads DRIVE, even when wiggling shifter. If it doesn't, check for intermittent contact at neutral safety switch.
- This tests for a faulty ECM.