C-1A ~ Park/Neutral Position (PNP) Switch

Chart C-1A Circuit Diagram:

Diagnostic Chart C-1A Park/Neutral Switch:

CIRCUIT DESCRIPTION:

The Park/Neutral switch contacts are a part of the Neutral start switch assembly. They are closed to ground in Park or Neutral and open in drive ranges. The ECM supplies voltage through a current limiting resistor to PNK/BLU wire and senses a closed switch when the voltage on PNK/PPL wire drops to less than one volt. The ECM uses the P/N signal as one of the inputs to control idle air, VSS diagnostics, and EGR. If PNK/BLU wire indicates P/N (grounded), while in drive range, the EGR would be inoperative, resulting in possible detonation. If PNK/BLU wire 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 the diagnostic chart.

1. Checks for a closed switch to ground in Park position, different makes of scan tools will read P/N differently.

2. Checks if PNK/BLU wire between ECM terminal B11 and neutral relay is open.

3. Checks if inhibitor is working properly.

4. Check for an open in the power feed circuit.