Code 31, Park/Neutral Switch CKT: Notes
NOTE:
Complete diagnosis of Code 31 for "H" body vehicles requires GM Tech 1 "Scan" tester, which is capable of indicating status of all 4 park/neutral switch positions. This chart does not apply to (VIN L) "H" body vehicles. Schematics for these models are supplied for reference purposes only.
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 29 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 open switch in Drive.
- Be sure "Scan" tester indicates Drive, even when wiggling shifter.