Transmission Position Sensor/Switch: Testing and Inspection

Chart C-1A Park/Neutral Switch:

Wiring Diagram for Chart C-1A Park/Neutral Switch:

CHART C-1 A PARK/NEUTRAL SWITCH DIAGNOSIS (PORT)


Circuit Description:
The park/neutral switch contacts are a part of the neutral start switch and are closed to ground in park or neutral, and open in drive ranges. The ECM supplies ignition voltage through a current limiting resistor to CKT 434 and senses a closed switch when the voltage on CKT 434 drops to less than one volt. The ECM uses the P/N signal as one of the inputs to control:


VSS diagnostics
Idle Air Control
EGR


If CKT 434 indicates P/N (grounded), while in drive range, the EGR would be inoperative, resulting in possible detonation. If CKT 434 indicates drive (open) a dip in the idle may exist when the gear selector is moved into drive range.


Test Description: Numbers below refer to circled numbers on diagnostic chart.
1. Checks for a closed switch to ground in park position. Different makes of "Scan" tools will read P/N 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 "Scan" indicates drive, even while wiggling shifter, to test for an intermittent or misadjusted switch in drive or overdrive range.