Transmission Position Sensor/Switch: Testing and Inspection

Chart C-1A - Park/Neutral (P/N) Switch Diagnosis (Auto Transmission Only):

Wiring Diagram For Chart C-1A - Park/Neutral (P/N) Switch Diagnosis (Auto Transmission Only):

CHART C-1A - PARK/NEUTRAL SWITCH DIAGNOSIS (AUTO TRANS. ONLY)


Circuit Description:

The Park/Neutral (P/N) 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 PIN signal as one of the inputs to control:

Idle Air Control (IAC)
Vehicle Speed Sensor (VSS) Diagnostics


Test Description: Numbers below refer to circled numbers on the 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 Operations" manual for type of display used.

2. Checks for an open switch in drive range.





3. Be sure "Scan" tool indicates drive, even while wiggling shifter to test for an intermittent or misadjusted switch in drive range.