Transmission Position Sensor/Switch: Testing and Inspection

Chart C-1A:

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.