Pontiac Fiero 1988 Service Manual page 661

6E3-C1-12 DRIVABILITY AND EMISSIONS - FUEL INJECTION (PORT)
P/N SWITCH
CONNECTOR
HARNESS CONNECTOR
FRONT U S J V I E W
PARK/NEUTRAL
SWITCH
ECM
NEUTRAL START
AND BACK-UP
SWITCH
TRANSAXLE
MOUNTED
ORN/BLK434 j
B 1 0
450
3
5-22-87
CIRCUIT TO GROUND IN
PARK AND NEUTRAL
W
AJW~ 12V
P/N SIGNAL
5-8-87
5S1545-6E
CHART C-1 A
PARK/NEUTRAL SWITCH DIAGNOSIS
(AUTO TRANSAXLE ONLY)
2.81 "P" SERIES (PORT)
C i r c u i t D e s c r i p t i o n :
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.
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 one volt.
The ECM uses the P/N signal as one of the inputs to control;
Idle Air Control
Vehicle Speed Sensor Diagnostics
Exhaust Gas Recirculation
If CKT 434 indicates P/N (grounded) while in drive range the EGR would be inoperative resulting in
possible detonation.
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 3. Be sure "Scan" indicates drive even while
numbers on the diagnostic chart. wiggling shifter to test for an intermittent or
1. Checks for a closed switch to ground in park misadjusted switch in drive,
position. Different makes of "Scan" tools will read
P/N differently. Refer to tool operators manual for
type of display used for a specific tool.
2. Checks for an open switch in drive range.
r