J2000/Sunbird V6-191 3.1L VIN T MFI (1994)
Park/Neutral Position Switch Circuit
Circuit Description:
The Park/Neutral Position (PNP) switch contacts shown are a part of the Park/Neutral position switch and are closed to ground in park or neutral,
and open in drive ranges.
The PCM supplies ignition voltage through a pull up resistor to CKT 434 and senses a closed switch when the voltage on CKT 434 drops to less than
one volt.
The PCM uses the PNP signal as one of the inputs to control:
^
Idle speed.
^
VSS diagnostics.
^
EGR.
If CKT 434 indicates PNP (grounded), while in drive range, the EGR would be inoperative, resulting in possible detonation.
If CKT 434 indicates drive (open) a sag in the idle may occur when the gear selector is moved into drive range.
Test Description: Number(s) below refer to circled number(s) on the diagnostic chart.
1. Checks for a closed switch to ground in park position. Different makes of scan toots will display the PNP switch differently. Refer to tool
operator's manual for type of display used for a specific tool.
2. Checks for an open switch in drive range.
3. Be sure Tech 1 scan tool indicates drive, even while wiggling shifter, to test for an intermittent or misadjusted switch in drive range.
