Chart C-1A Park/Neutral Switch Diagnosis

Park/Neutral Circuit:

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 P/N signal as one of the inputs to control:

^ Idle Air Control (IAC).

^ Vehicle Speed Sensor (VSS) Diagnostics.

Park/Neutral Diagnostic Chart C-1A:

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" tools will read PIN differently. Refer to "Tool Operations" manual for type of display used.

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.