Chart C-1A Park/Neutral Switch Diagnosis

Chart C-1A:

Park/Neutral Position Switch Circuit:

CIRCUIT DESCRIPTION
The Park/Neutral Position (PNP) switch contacts are closed to ground in park and neutral When the gear selector is positioned in reverse or drive range, the PNP switch will open and the PCM will interpret this signal as drive or reverse.

The Powertrain Control Module (PCM) uses the PNP signal as one of the inputs to control:

^ Idle Air Control (IAC).
^ Vehicle Speed Sensor (VSS) diagnostics.
^ Exhaust Gas Recirculation (EGR).

If CKT 434 indicates PNP (grounded), while in drive range, the EGR would be inoperative, resulting in possible detonation.

If CKT 434 always indicates drive (open), a drop in the idle speed may exist when the gear selector is moved into drive range.

DIAGNOSTIC TROUBLE CODE (DTC) CHART TEST DESCRIPTION
Numbers below refer to circled numbers on the diagnostic chart.

1. Checks for a closed switch to ground in park position.
2. Checks for an open switch in drive range.
3. Make sure the Tech 1 Scanner indicates drive, even while wiggling shifter to test for an intermittent or misadjusted switch in drive range.

DIAGNOSTIC AIDS
PNP relay is located in the Instrument Panel relay center on driver's side of dash.