1988 PONTIAC FIERO Service Repair Manual

6E2-A-6 5.8% (VIN E) DRIVEABILITY AND EMISSIONS
FUEL INJECTION ECM CONNECTOR IDENTIFICA"F0N
This ECM voltage chart is for use with a digital voltmeter to further aid in diagnosis. The voltages
you get may vary due to low battery charge
or other reasons, but they should be very close.
THE FOLLOWING CONDITIONS MUST
BE MET BEFORE TESTING:
@ Engine at operating temperature e Engine idling in closed loop (for "Engine Run" column)
r Test terminal not grounded e ALDL tool not installed
VOLTAGE
I
B + 1 B + I EGRCONTROLSOLI A4 I GRY
I I "SERVICE ENGINE I
1 1 1 A.I.R. DIVERT I I BLW I
o 10 1 4 TH GEAR I c7 ILT BLU
4.75 1.1 MAP SIGNAL C11 LT GRN
24 PIN A-B CONNECTOR
32 PIN C-D CONNECTOR
( 012 I NOT USED I I
BLW WHT Dl SYSTEMGROUND 0
PPL I D2 I MAPGROUND 10 10 I
BLK I D5 I BYPASS
D9 NOT USED I I I I Dl0 I NOT USED I I I
I Dl1 I NOT USED I I
LT GRN I DI~ I INJECTOR B l e+ IB+
Dl5 NOTUSED
LT BLU Dl6 INJECTORA B+ B+
1 Var~es from 60 to battery voltage, 6 Reads battery voltage in gear
depending
on positlon of drive wheels 7 12 volts, when englne IS crank~ng
2 12 V for f~rst two seconds.
3 Varies
4 12V when fuel pump is running
5 Var~es with temperature
ENGINE 5.0 L
Figure A-5 - ECM Connector Terminal End View 5.OL (VIN E)

BLANK

6E2-A-8 S.OL (VIN E) DRIVEABILITY AND EMISSIONS
DIAGNOSmIC CIRCUIT CHECK
The Diagnostic Circuit Check is an organized approach to identifying a problem created by an electronic
engine control system malfunction. It must be the starting point for any driveability complaint diagnosis,
because it directs the service technician to the next logical step in diagnosing the complaint.
The "Scan Data" listed in the table may be used for comparison, after completing the diagnostic circuit check
and finding the on-board diagnostics functioning properly and no trouble codes displayed. The "Typical Values"
are an average of display values recorded from normally operating vehicles and are intended to represent what a
normally functioning system would typically display.
A "SCAN" TOOL THAT DISPLAYS FAULTY DATA SHOULD NOT BE USED, AND THE PROBLEM
SHOULD BE REPORTED TO THE MANUFACTURER. THE USE OF A FAULTY "SCAN" CAN RESULT
IN MISDIAGNOSIS AND UNNECESSARY PARTS REPLACEMENT.
Only the parameters listed below are used in this manual for diagnosis. If
a "Scan" tool reads other
parameters, the values are not recommended by General Motors for use in diagnosis. For more description on the
values and use of the "Scan" to diagnosis ECM inputs, refer to the applicable diagnosis section in Section
"C". If
all values are within the range illustrated, refer to "Symptoms" in Section
"B".
""SCAN" DATA
Idle / Upper Radiator Hose Hot / Closed Throttle / Park or Neutral /Closed Loop / Acc. off
"SCAN" Position Units Displayed Typical
Data Value
Coolant Temp. CO 85" - 105"
TPS Volts .4 - 1.25
MAP Volts
1 - 2 (depends on Vac. & Baro pressure)
INT (Integrator) Counts Varies
BLM (Block Learn) Counts 118- 138
IAC Counts (steps) 1-50
RPM RPM 1000
k 75 RPM (depends on temperature)
0 2 Volts .001 - 999 and varies
OpenIClosed Loop OpenICIosed Closed Loop (may go open with extended idle)
A/C Request YesINo No (yes, with A/C requested)
PIN Switch PIN and RDL
ParkINeutral (PIN)
TCC
On/Off Off1 (on, with TCC commanded)
VSS MPH 0
Battery Volts 13.5- 14.5
Air Switch NormalIDivert Normal
Air Divert ConverterIPort Converter
Knock Signal
YesINo N o
4th Gear
YesINo No (Yes, if in 4th Gear)
MAT Temp.
CO 10" - 90" ( Depends on Under Hood Temp.).
Power Steering Pressure Switch
NormalIHi Pressure Normal

DRIVEABILITY AND EMISSIONS 5.OL (VIN E) 6EZ-A-9
I SEE CHART A-2 4- ---------- 2

6EZ-A-10 5.0L (VIN E) DRIVEABILITY AND EMISSIONS
TO OIL PRESS. SW.
&FUEL PUMP RELAY
BATTERY
12 V
. . . . . . . . FUSIBLE LINK 15 WAY
439 PNWBLK
419
BRNNVHT
SERIAL DATA
451
WHTIBLK
450 BLWHT
ALDL CONNECTOR
NO "SERVICE ENGINE SOON" "LIGHT
5.OL (VIN E) "F'" SERIES (TBI)
Circuit Description:
There should always be a steady "Service Engine Soon" light, when the ignition is "ON" and engine stopped.
Battery is supplied directly to the light bulb.
The electronic control module (ECM) will control the light and
turn it "ON" by providing a ground path through CKT 419 to the ECM.
Test Description: Numbers below refer to circled
numbers on the diagnostic chart.
1. Battery feed CKT 340 is protected by a
20amp in-
line fuse. If this fuse was blown, refer to wiring
diagram on the facing page of Code 54.
2. Using a test light connected to 12 volts, probe each
of the system ground circuits to be sure
a good
ground is present. See ECM terminal end view in
front of this section for ECM pin locations of
ground circuits.
Diagnostic Aids:
Engine runs ok, check:
@ Faulty light bulb
@ CKT419open
@ Gage fuse blown. This will result in no oil, or
generator lights, seat belt reminder, etc.
Engine cranks, but will not run.
@ Continuous battery - fuse or fusible link open.
@ ECM ignition fuse open.
@ Battery CKT 340 to ECM open.
o Ignition CKT 439 to ECM open.
@ Poor connection to ECM.

DRIVEABILITY AND EMISSIONS 5.OL (VIN E) 6EZ-A-11
@ DISCONNECT ECM CONNECTORS.
@ IGNITION "ON".
@ PROBE CKT 419, WlTH TEST LIGHT
TO GROUND.
- GAGE FUSE. IGNITION "ON". SHORT TO GROUND IN
- FAULTY BULB. 0 PROBE CKT 340 81 439 CIRCUIT THAT HAD A
- OPEN CKT 419. WITH TEST LIGHT TO
- CKT419 SHORTED TO

6E2-A-12 5.OL (VIN E) DRIVEABILITY AND EMISSIONS
TO OIL PRESS. SW. ECM
&FUEL PUMP RELAY
FUSE
& HOLDER BATTERY 12 V . . . . . . . .
FUSIBLE LINK
439
PNWBLK
419 BRNNVHT
- -
451 WHTIBLK
450
BLWHT
ALDL CONNECTOR
8-4-87
55 1235-6E
CHART A-2
NO ALDL DAM OR WON"T FLASH CODE 12
'SERVICE ENGINE SOON" LLlGHT "ON" "STEADY
5.OL (VIN E) "F" "SERIES (TBI)
Circuit Description:
There should always be a steady "Service Engine Soon" light, when the ignition is "ON" and engine stopped.
Battery is supplied directly to the light bulb. The electronic control module
(ECM) will turn the light "ON" by
grounding CKT 419 at the ECM.
With the diagnostic terminal grounded, the light should flash
a Code 12, followed by any trouble code(s)
stored in memory.
A steady light suggests a short to ground in the light control CKT 419, or an open in diagnostic CKT 451.
Test Description: Numbers below refer to circled
numbers on the diagnostic chart.
1. If there is a problem with the ECM that causes
a
"Scan" tool to not read serial data, then the ECM
should not flash a Code
12. If Code 12 does flash,
be sure that the "Scan" tool is working properly on
another vehicle. If the "Scan" is functioning
properly and CKT 461 is OK, the PROM or ECM
may
be at fault for the NO ALDL symptom.
2. If the light goes "OFF" when the ECM connector is
disconnected, then CKT 419 is not shorted to
ground.
3. This step will check for an open diagnostic CKT
45 1.
4. At this point, the "Service Engine Soon" light
wiring is OK. The problem is a faulty ECM or
PROM. If Code 12 does not flash, the ECM should
be replaced using the original PROM. Replace the
PROM only after trying an ECM, as a defective
PROM is an unlikely cause of the problem.

DRIVEABILITY AND EMISSIONS 5.OL (VIN E) 6E2-A-13
DISCONNECT ECM CONNECTORS.
CHECK SERIAL DATA CKT461 FOR OPEN OR
IGNITION "ON" AND NOTE
SHORT TO GND. BETWEEN ECM AND ALDL
@ IGNITION "ON", ENGINE STOPPED.
KT 451, WITH TEST
IF OK, REPLACE ECM USING ORIGINAL PROM.
TERMS. "B" AND CKT451 TO ECM.