Fastener
Torque Specs
Cylinder Head Tightening Sequence
Intake Manifold
Tightening Sequence
Firing Order
Other Tools
OBD I Trouble Codes
Decoding your VIN
Park / Neutral Switch Circuit
The computer supplies ignition voltage through a current limiting resistor to the P/N signal circuit to the computer and senses a closed switch when that circuit's voltage drops to less than one volt.
The ECM uses the P/N signal as one of the inputs to control:
- Idle Speed (IAC)
- Vehicle Speed Sensor Diagnostics (VSS)
- Spark Advance
Code 31 will set if:
- P/N Signal Circuit indicates a ground for 3 consecutive starts
or if:
- P/N Signal Circuit indicates a ground
- No Code 38
- Transmission is in high gear
- VSS greater than 45 mph and TPS less than 15% (.94 volt)
- Above conditions are met for 12 seconds
