Chart C1A - Park/Neutral Switch Check (Auto Trans Models)
The park/neutral switch contacts are part of neutral start switch, are closed to ground in park or neutral, and open in drive ranges. The ECM supplies ignition voltage through a current limiting resistor to circuit No. 434, and senses a closed switch when voltage on circuit No. 434 drops to less than one (1) volt. The ECM uses this signal as one of the inputs to control IAC and VSS diagnostics.
NOTE:
The following step numbers refer to the step numbers in the accompanying Flow Chart.
- Checks for closed switch to ground in park position. Use an ohmmeter instead of a test light to 12 volts. Resistance will be low indicating continuity to ground.
- Checks for an open switch in drive range. Use an ohmmeter instead of a test light to 12 volts. Resistance will be high or infinity, indicating an open switch.
- Checks to this point indicate park/neutral switch and wiring are okay. The ECM signal voltage on circuit No. 434 may be missing. To check, reconnect ECM. Either back probe ECM connector circuit No. 434 with selector in drive or disconnect park/neutral switch. Probe harness connector circuit No. 434 with a voltmeter to ground.