1988 PONTIAC FIERO Service Repair Manual

BRAKE SWITCH
TANIBLK 456
DK GRNIY EL 428
TEMP.SWITCH
TANNVHT 250

DRIVEABILITY AND EMISSIONS 5.BL (VIN F) & 5.7L(VlN 8) 6E3-A-7
PORT FUEL INJECTION ECM CONNECTOR IDEN"II"IFICATI0IV
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.
B + in Chart refers to system voltage.
THE FOLLOWING CONDITIONS MUST
BE MET BEFORE TESTING:
@ Engine at operating temperature @ Engine idling in "Closed Loop" (for "Engine Run" column) in
park or neutral
e Test terminal not grounded @ "Scan" tool not installed
VOLTAGE
CONNECTOR
CONNECTOR
* Lessthan .5 volts.
1. Varies from .60 to battery voltage depending on position of drive wheels.
3. 12V First two seconds.
Figure
A-6 - ECM Connector Terminal End View - 5.OL (VIN F) & 5.7L (VIN 8) "F" Series

6E3-A-8 5.OL (VIN F) & 5.7L(VIN 8) DRIVEABILITY AND EMISSIONS
DIAGNOSIC CIRCUIXCHECK
The Diagnostic Circuit Checlc 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 diagnosing. If a "Scan" reads other parameters,
the values are not recommended by General Motors for use in diagnosing. 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
Desired RPM RPM ECM ~dle command (vanes w~th temp.)
RPM RPM
+ 100 RPM from desired RPM ( k 50 ~n drive)
Coolant Temp.
CO 85" - 105"
MAT Temp. CO 10" - 90" (depends on underhood temp.)
MAF G
m/Sec 4-7
Air Flow
Gm/Sec 4 - 7
BPW (base pulse width)
M/Sec 1 - 4 and varying
02 Volts 1 - 1000 and varying
TPS Volts 46 - .62
I AC Counts (steps)
5 - 50
INT (Integrator) Counts
Vanes
BLM (Block Learn) Counts 118- 138
Open/Closed Loop Open/Closed Closed Loop (may go open with extended idle)
BLM Cell Cell Number
0 or 1 (depends on Air Flow & RPM)
VSS MPH 0
TCC
On/Off Off/ (on wlth TCC commanded)
Battery Volts 13.5
- 14.5
PPSW
Volts 13.5- 14.5
LV8 Counts 30
- 60
Knock Retard Degrees
of Retard 0
Spark Advance
# of Degrees Varies
PIN
Swltch PIN and RDL ParkINeutral (PIN)
A.I. R. Control
Normal/Divert Normal
A.I.R. Switch
PortIConverter Converter
NC Request Yes/No No (yes, wlth NC requested)
Fan Request
Yes/No No (yes, with NC high pressure)
EGRDC 0- 100%
0 at idle
EGR Diagnostic
On/Off off
Fan
OnIOff Off (below 108°C)
CCP duty cycle 0
- 100% 0
Knock Signal
YesINo No (yes, when knock is detected)
Shift Light
(MIT) On/Off Off
4th Gear
Yes/No No (yes, when in 4th gear)

DRIVEABILITY AND EMISSIONS 5.0L(VIN F) & 5.7L(VIN 8) 6E3-A-9

TO MAF SENSOR
POWER & BURN-OFF
RELAY, OIL PRESS. SW.
.....-
439 PNKIBLK
419 BRNNVHT
SERIAL DATA
451 WHTIBLK
450
BLWHT
ALDL CONNECTOR
CHART A - 1
NO "'SERVICE ENGINE SOON" LIGHT
5.OL (VIN F) & 5.7L (VIN 8) "F'XSEBIE'S (PORT)
Circuit Description:
There should always be a steady "Service Engine Soon" light when the ignition is "ON" and engine stoppccl.
Ignition voltage 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. If the fuse in holder is blown, refer to facing page
of Code
54 for complete circuit.
2. Using a test light connected to 12 volts probe each
of the system ground circuits to be sure a good
ground is present. Refer to the ECM terminal end
view in front of this section for ECM pin locations
of ground circuits.
Diagnostic Aids:
Engine runs OK, check:
r Faulty light bulb.
@ CKrI' 419 open.
@ Gage fuse blown. This
will result in no oil or
generator lights, seat belt reminder, etc.
Engine cranks but will not run, check:
r Continuous battery - fuse or fusible link open.
@ ECM ignition fuse open.
r Battery CKT 340 to ECM open.
@ Ignition CKT 439 to ECM open.
@ Poor connection to ECM.

DRIVEABILITY AND EMISSIONS 5.0L (VIN F) & 5.7L (WIN 8) 6E3-A-11
@ DISCONNECT ECM CONNECTORS.
e IGNITION "ON"
PROBE
CKT419, WITH TEST LIGHT
TO GROUND.
- GAGE FUSE
- FAULTY BULB PROBE
CKT 340 & 439 CKT
THAT HAD A
- OPEN CKT 419 WITH TEST LIGHT TO
- CKT 419 SHORTED TO
IS THE LIGHT "ON" ON
- OPEN IGN. FEED TO
HAT DID NOT LIGHT

6E3-A-12 5.OL (VIN F) & 5.7L (VIN 8) DRIVEABILITY AND EMISSIONS
TO MAF SENSOR
POWER & BURN-OFF
, . . . . .
439 PNWBLK
419 BRNNVHT
SERIAL DATA
451
WHTIBLK
450 BLKIWHT
ALDL CONNECTOR
CHART A-2
NO ALDL DATA OR WON'T FLASH CODE 12
""SERVICE ENGINE SOON" LIGHT '"ON" STEADY
5.OL (VIN F) & 5.7L (VIN 8) ""FYEERIES (PORT)
Circuit Description:
'I'here should always be a steady "Service Engine Soon" light when the ignition is "ON" and engine stopped.
Ignition voltage is supplied to the light bulb.
'I'he 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 tin open in cliagnostic 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, the ECM
should not flash a Code 12. If Code 12 is flashing
check for CKT 451 short to ground. 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
Mem-Cal or ECM may be at fault for the NO
ALDL symptom. 2.
If
the light goes
"OFF" when the ECM connector is
disconnected,
CK'r 419 is not shorted to ground.
3. This step will check for an open diagnostic
CKT 451.
-2. At this point the "Service Engine Soon" light
wiring is OK. The problem is a faulty ECM or
Mem-Cal. If Code 12 does not flash, the ECM
should be replaced using the original Mem-Cal.
Replace the Mem-Cal only after trying an ECM, as
a defective Mem-Cal is an unlikely cause of the
problem.

DRIVEABILITY AND EMISSIONS 5.0L(VIN F) & 5.7L(VIN 8) 6E3-A-13
CHART A-2
NO ALDL DATA OR WONT FLASH CODE 12
FAULTY ECM OR MEM-CAL.
OT GROUNDED.
CLEAR CODES AND CONFIRM "CLOSED LOOP
" OPERATION AND NO "SERVICE ENGINE SOON" LIGHT.