Transmission Position Sensor/Switch: Testing and Inspection

Chart C-1A:

Chart C-1A Wiring Diagram:

CIRCUIT DESCRIPTION:

The Park/Neutral Switch contacts 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
^ VSS Diagnostics
^ EGR


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 operators 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 mis-adjusted switch in drive range.

DIAGNOSTIC AIDS:

^ If CKT 434 indicates P/N (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 may exist when the gear selector is moved into drive range.