Lumina L4-151 2.5L (1991)
Wiring Diagram For Park/Neutral Switch
CIRCUIT DESCRIPTION:
The PARK/NEUTRAL switch contacts 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 434, and senses a closed switch when the voltage on circuit 434 drops to less than one volt. The ECM uses the P/N
signal as one of the inputs to control idle air and vehicle speed sensor diagnostics.
TEST DESCRIPTION: The numbers below refer to circled numbers on the diagnostic chart.
1.
Checks for a closed switch to ground in the park position. The use an ohmmeter instead of a test light to 12 volts (DO NOT use a live circuit using
an ohmmeter). The resistance will be low which indicates continuity to ground.
2.
Checks for an open switch in drive range. The use an ohmmeter instead of a test light to 12 volts (DO NOT use a live circuit using an ohmmeter).
The resistance will be high or infinity which indicates an open switch.
3.
Up to this point, the checks indicate that the P/N switch and wiring are OK, but the ECM signal voltage on circuit 434 may be missing. To check,
reconnect the ECM. Disconnect P/N switch and probe the harness connector circuit 434 with a voltmeter to ground.
