Skylark L4-138 2.3L DOHC VIN D MFI (1988)
Wiring Diagram for Chart C-1A - Park/Neutral Switch Diagnosis
CHART C-1A PARK/NEUTRAL SWITCH DIAGNOSIS
Circuit Description:
The Park/Neutral Switch contacts are a part of the Neutral Start switch and are closed to ground in park or neutral, and open in drive ranges and reverse.
The electronic control module (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 1 volt.
The ECM uses the P/N signal as one of the inputs to control:
Idle Air Control
Code 24 VSS Diagnostics
If CKT 434 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 display P/N differently. Refer to "Tool Operator's"
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 misadjusted switch in drive range.
