PONTIAC FIERO 1988 Service Repair Manual

6E3-A-58 5.OL (VIN F) & 5.7L (VIN 8) DRIVEABILITY AND EMISSIONS
PNKIBLK 439
PPL 963
5V
IP CONN.
DECODER
MODULE
CODE 46
VEHICLE ANTI-THEFT SYSTEM (VATS) CIRCUIT
5.OL (VIN F) & 5.7L (VIN 8) 'TF'3SERlES (PORT)
Circuit Description:
The VATS system is designed to disable vehicle operation if the incorrect key or starting procedure is used.
The VATS decoder module sends a signal to the ECM if the correct key is being used. If the proper signal does
not reach the ECM on CKT 963, the ECM will not pulse the injectors
"ON" and thus not allow the vehicle to be
started.
Code
46 will set, if the proper signal is not being received at ECM terminal "B6" when the ignition is turned
"ON". Code 46 does not store in the ECM memory but is only present when the conditions stated above are met.
Test Description: Numbers below refer to circled 2. If Code 46 is stored, and the engine will not crank,
numbers on the diagnostic chart. it indicates that there is a VATS problem or an
1. If the engine cranks, and a Code 46 is stored, it incorrect key or starting procedure is being used.
indicates that the portion of the module which
generates the signal to the ECM is not operating
or CKT 963 is open or shorted to ground. If the
decoder module is found to be
OK, as determined
from Section
"8AV, the ECM may be at fault, but
this is not a likely condition.

DRIVEABILITY AND EMISSIONS 5.OL (WIN F) & 5.7L (VIN 8) 6E3-A-59
I @ IGNITION "ON". I
PROBLEM IS INTERMITTENT. IF NO
OTHER CODE IS STORED, REFER TO
TO GROUND IN CKT
963.
IF OK, IT IS A FAULTY VATS
DECODER MODULE.

6E3-A-60 .5.0L (VIN F) & 5.7L (VIN 8) DRIVEABILITY AND EMISSIONS
340 - ORN
BULKHEAD CONN.
RELAY DRIVE
CODE 54
FUEL PUMP CIRCUIT
(LOW VOLTAGE)
5.OL (VIN F) & 5.7L (VIIN 8) "F" WRIES (PORT)
Circuit Description:
The status of the fuel pump CKT 120 (PPSW) is monitored by the ECM at terminal "H2" and is used to
compensate fuel delivery based on system voltage. This signal is also used to store a trouble code if the fuel
pump relay is defective or fuel pump voltage is lost while the engine is running. There should be about 12 volts
on CKT
120 for 2 seconds after the ignition is turned "ON", or any time references pulses are being received by
the ECM.
Code
54 will set, if the voltage at terminal "R2" is less than 2 volts for 1.5 seconds since the last reference
pulse was received. This code is designed to detect a faulty relay, causing extended crank time, and the code
will help the diagnosis of an engine that
"CRANKS BUT WILL NOT RUN".
If a fault is detected during start-up, the "Service Engine Soon" light will stay "ON" until the ignition is
cycled "OFF". However, if the voltage is detected below
2 volts, with the engine running, the light will only
remain "ON" while the condition exists.

DRIVEABILITY AND EMISSIONS 5.OL (VIN F) & 5.7L (VIN 8) 6E3-A-61
ONNECT FUEL PUMP
E LIGHT WITHIN 2
@ OIL PRESSURE NORMAL.

6E3-A-62 5.OL (VIN F) & 5.7L (VIN 8) DRIVEABILITY AND EMISSIONS
5.OL (VIN F) & 5.7L (VIN 8)
CODE 51
MEM-CAL ERROR
(FAULTY OR INCORRECT MEM-CAL)
IF OK, REPLACE MEMICAL, CLEAR MEMORY, AND RECHECK. IF CODE 51 REAPPEARS, REPLACE ECM.
CLEAR CODES AND CONFIRM "CLOSED LOOP" OPERATION AND NO "SERVICE ENGINE SOON" LIGHT.
CODE 52
CALPAK ERROR
(FAULTY OR INCORRECT CALPAK)
SOCKET. IF OK, REPLACE MEM-CAL, CLEAR MEMORY, AND RECHECK.
CLEAR CODES AND CONFIRM "CLOSED LOOP" OPERATION AND NO "SERVICE ENGINE SOON" LIGHT.
CODE 53
SYSTEM OVER VOLTAGE
CODE 53 WILL SET, IF VOLTAGE AT ECM IGNITION INPUT PIN IS GREATER THA
17.1 VOLTS FOR 2 SECONDS.

DRIVEABILITY AND EMISSIONS 5.OL (VIN F) & 5.7L (VIN 8) 6E3-B-1
SYMPTOMS
TABLE OF CONTENTS
............................................................. Before Starting Page B-I
lntermittents............................................................... PageB-2
...................................................... Hesitation, Sag, Stumble Page 8-3
....................................................... Surges and/or Chuggle Page B-3
.............................................. Lack of Power, Sluggish, or Spongy Page 8-4
Detonation/SparkKnock ...................................................... PageB-4
Cuts Out, Misses
............................................................ Page B-5
Backfire................................................................... PageB-5
.......................................................... Poor Fuel Economy Page 8-6
.......................................................... Dieseling, Run-on,. Page B-6
........................................ Rough, Unstable, or Incorrect Idle, Stalling Page B-6
............................................. Excessive
Exhaust Emissions or Odors Page B-7
Restricted Exhaust System Check (Chart
B-1) ....................................... Page 8-8
BEFORE STARTING
Before using this section you should have
performed the DIAGNOSTIC CIRCUIT CHECK
and found out that:
1. The ECM and "Service Engine Soon" light are
operating.
2. There are no trouble codes stored, or there is a
trouble code but no "Service Engine Soon" light.
Verify the customer complaint, and locate the
correct SYMPTOM below. Check the items
indicated under that symptom.
If the ENGINE CRANKS BUT WILL NOT
RUN, see CHART A-3.
Several of the symptom procedures below call
for a Careful Visual Check. This check should
include:
@ ECM grounds for being clean and tight
@ Vacuum hoses for splits, kinks, and proper
connections, as shown on Emission Control
Information label.
@ Air leaks at throttle body mounting and intake
manifold.
@ Air leaks between MAF sensor and throttle
body.
@ Ignition wires for cracking, hardness, proper
routing, and carbon tracking.
@ Wiring for proper connections, pinches, and cuts.
The importance of this step cannot be stressed
too strongly
- it can lead to correcting a problem
without further checks and can save valuable time.

6E3-B-2 5.OL (VIN F) & 5.7L (VIN 8) DRIVEABILITY AND EMISSIONS
Problem may or may not turn "ON" the "Service Engine Soon" light, or store a code.
DO NOT use the Trouble Code Charts in
An intermittent "Service Engine Soon" light
Section A for intermittent problems. The fault must
with no stored code may be caused by:
be present to locate the problem. If a fault is
@ Ignition coil shorted to ground and arcing at
intermittent, use of Trouble Code Charts
may result
spark plug wires or plugs.
in replacement of good parts.
"Service Engine Soon" light wire to
ECM
@ Most intermittent problems are caused by
shorted to ground. (CKT 419).
faulty electrical connections or wiring. Perform
Diagnostic "Test" Terminal wire to ECM,
careful check as described at start of Section
shorted to
ground.(CKT 451)
"B". Check for:
@ ECM power grounds. See ECSI wiring
@ Poor mating of the connector halves, or diagrams.
terminals not fully seated in the connector
@ Loss of trouble code memory. To check,
body (backed out). disconnect TPS and idle engine until "Service
@ Improperly formed or damaged terminals.
Engine Soon" light comes on. Code 22 should be
All connector terminals in problem circuit
stored, and kept in memory when ignition is
should be carefully reformed or replaced to turned "OFF". If not, the ECM is faulty.
insure proper contact tension.
@ Check for an electrical system interference
@ Poor terminal to wire connection. This caused by a defective relay, ECM driven
requires removing the terminal from the
solenoid, or switch. They can cause a sharp
connector body to check. See "Introduction"
electrical surge. Normally, the problem will
to Section
"6E". occur when the faulty component is operated.
@ If a visual check does not find the cause of the @ Check for improper installation of electrical
problem, the car can be driven with a voltmeter
options, such as lights,
%way radios, etc.
connected to
a suspected circuit. A "Scan" tool
EST wires should be kept away from spark plug
can also be used for monitoring input signals to wires, distributor wires, distributor housing,
the ECM to help detect intermittent conditions. coil, and generator. Wire from
ECM to
An abnormal voltage, or "Scan" reading, when distributor
(CKT 453) should be a good
the problem occurs, indicates the problem
may connection.
be in that circuit. If the wiring and connectors
@ Check for open diode across AIC compressor
check OK and a Trouble Code was stored for a
clutch, and for other open diodes (see wiring
circuit having a sensor, except for Codes
43, 44, diagrams).
and 45, substitute a known good sensor and
recheck.
HARD START
Definition: Engine cranks OK, but does not start for a long
time. Does eventually run, or may start but immediately dies.
Perform careful check as described at start of
Section
"B".
@ Make sure driver is using correct starting
procedure.
@ CHECK:
- TPS for sticking or binding or a high TPS
voltage with the throttle closed (should read
less than
.700 volts).
- High resistance in coolant sensor circuit or
sensor itself. See Code 15 chart or with
a
"Scan" tool compare coolant temperature with
ambient temperature on a cold engine.
- Fuel pressure CHART A-7.
- Water contaminated fuel.
- EGR operation. Be sure valve seats properly and
is not staying open. See CHART C-7.
- Both injector fuses (visually inspect).
- Ignition system - Check distributor for:
Proper Output with ST-125.
Worn shaft.
Bare and shorted wires.
Pickup coil resistance and connections.
Loose ignition coil ground.
Moisture in distributor cap.
@ If problem exists in cold weather, check cold start
valve. See CHART A-9.

DRIVEABILITY AND EMISSIONS 5.OL (VIN F) & 5.7L (VIN 8) 6E3-8-3
@ A faulty in-tank fuel pump check valve will @
allow the fuel in the lines to drain back to the
tank after the engine is stopped. To check for
this condition:
e
Perform Fuel System Diagnosis, CHART A-7.
@ Remove spark plugs. Check for wet plugs,
cracks, wear, improper gap, burned electrodes,
@
or heavy deposits. Repair or replace as
necessary. If
engine starts but then immediately stalls
open distributor by-pass line. If engine then
starts and runs OK, replace pickup coil.
If engine starts and stalls disconnect MAF
sensor. If engine then
r~lns and sensor
connections are OK, replace
thr. )t.ft+rl'.
Basic engine problem.
HESITATION, SAG, STUMBLE
Definition: Momentary lack of response as the accelerator i., pl,ihcc! dowt-
Can occur at all car speeds. Usually most severe when first tryine, lo m,tlir. LII~.
car move, as from a stop sign. May cause the engine to sta!! 1, e er., riu~~~!~
s Perform careful visual check as described at
start of Section
"B".
@ CHECK:
- Fuel pressure. See CHART A-7. Also, check
for water contaminated fuel.
- Air leaks at air duct between MAF sensor and
throttle body.
- Spark plugs for being fouled or faulty wiring.
- Mem-Cal number. Also check service bulletins
for latest Mem-Cal.
- TPS for binding or sticking. Voltage should
increase at
a steady rate as throttle is moved
toward WOT.
- Ignition timing. See emission control
information label.
- Generator output voltage. Repair if less than 9
or more than 16 volts.
- HE1 ground, CKT 453.
- Canister purge system for proper operation.
See CHART C-3.
- EGR - See CHART C-7.
e Perform injector balance test CHART C-2A.
SURGES AND/OR CHUGGLE
Definition: Engine power variation under steady
throttle or cruise. Feels like the car speeds up and
slows down with no change in the accelerator pedal.
@ Be sure driver understands transmission
converter clutch and
AJC compressor operation
in owner's manual.
Perform careful visual inspection as described
at start of Section
"B".
e CHECK:
- Loose or leaking air duct between MAF sensor
and throttle body.
- Generator output voltage. Repair if less than 9
or more than 16 volts.
- EGR - There should be no EGR at idle. See
CHART C-7.
- Vacuum lines for kinks or leaks.
- Ignition timing. See emission control
information label.
- In-line fuel filter. Replace if dirty or plugged.
- Fuel pressure while condition exists. See
CHART A-7.
@ Inspect oxygen sensor for silicon contamination
from fuel, or use of improper RTV sealant. The
sensor may have a white, powdery coating and
result in a high but false signal voltage (rich
exhaust indication). The ECM will then reduce
the amount of fuel delivered to the engine,
causing a severe driveability problem.
@ Remove spark plugs. Check for cracks, wear,
improper gap, burned electrodes, or heavy
deposits. Also check condition of distributor
cap, rotor, and spark plug wires.
@ To help determine if the condition is caused by a
rich or lean system, the car should be driven at
the speed of the complaint. Monitoring block
learn at the complaint speed will help identify
the cause of the problem.
If the system is lean
(block learn greater than
1381, refer to
"Diagnostic Aids"
on facing page of Code 44. If
the system is running rich (block learn less than
1181, refer to "Diagnostic Aids" on facing page
of Code
45.

6E3-B-4 5.OL (VIN F) & 5.7L (VIN 8) DRIVEABILITY AND EMISSIONS
LACK OF POWER, SLUGGISH, OR SPONGY
Definition: Engine delivers less than expected power. Little or
no increase in speed when accelerator pedal is pushed down part way.
@ Perform careful visual check as described at
start of Section "B".
@ Compare customer's car to similar unit.
Make sure the customer's car has an actual
problem.
@ Remove air cleaner and check air filter for
dirt, or for being plugged. Replace as
necessary.
@ CHECK:
- For loose or leaking air duct between MAF
sensor and throttle body.
- Ignition timing. See emission control
information label.
- Restricted fuel filter, contaminated fuel or
improper fuel pressure. See CHART A-7.
- ECM Ground circuits - See ECM wiring
diagrams.
- EGR operation for being open, or partly open
all the time
- CHART C-7.
- Exhaust system for possible restriction: See
CHART
B-1.
- Inspect exhaust system for damaged or
collapsed pipes.
- Inspect muffler for heat distress or possible
internal failure.
- For possible plugged catalytic convertor by
comparing exhaust system backpressure on
each side at engine. Check backpressure by
removing
A.1.R check valves near exhaust
manifolds. See CHART
B-1 for procedure.
- Generator output voltage. Repair if less than 9
or more than 16 volts.
- Engine valve timing and compression.
- Engine for proper or worn camshaft. See Section
"6A".
- Secondary voltage using a shop ocilliscope or a
spark tester
5-26792 (ST-125) or equivalent.
- Check for excessive knock retard. See CHART
C-5.
DETONATION ISPARK KNOCK
Definition: A mild to severe ping, usually worse under
acceleration. The engine makes sharp metallic knocks that
change with throttle opening. Sounds like popcorn popping.
@ Check for obvious overheating problems:
- Low coolant.
- Loose water pump belt.
- Restricted air flow to radiator, or restricted
water flow thru radiator.
- Inoperative electric cooling fan circuit. See
CHART C-12.
@ CHECK:
- Ignition timing. See vehicle emission control
information label.
- EGR system for not opening - CHART C-7.
- TCC operation - CHART C-8.
- Fuel system pressure. See CHART A-7.
- Mem-Cal - Be sure it's the correct one. (See
"Service Bulletins").
- Valve oil seals for leaking.
@ Check for incorrect basic engine parts such as
cam, heads, pistons, etc.
@ Checkforpoorfuelquality.
@ Remove carbon with top engine cleaner. Follow
instructions on can.
@ Check ESC system
See CHART C-5
@ To help determine if the condition is caused by a
rich or lean system, the car should be driven at
the speed of the complaint. Monitoring block
learn at the complaint speed will help identify the
cause of the
problem. If the system is runnig lean
(block learn greater than
1381, refer to
"Diagnostic Aids" on facing page of Code
44. If
the system is running rich (block learn less than
1181, refer to "Diagnostic Aids" on facing page of
Code 45.

DRIVEABILITY AND EMISSIONS S.OL (VIN F) & 5.7L (VIN 8) 6E3-B-5
Definition: Steady pulsation or jerking that follows engine
speed, usually more pronounced as engine load increases. The
exhaust has
a steady spitting sound at idle or low speed.
@ Perform careful visual check as described at blink
at any connector, it is a faulty injector drive
start of Section
"B". circuit harness, connector, or terminal.
@ Check for missing cylinder by: @ Perform the Injector Balance Test. See CHART
1. Disconnect IAC valve. Start engine. C-2A.
Remove one spark plug wire at a time
@ CHECK:
using insulated pliers. - Spark plug wires by connecting ohmmeter to
2. If there is an rpm drop on all cylinders ends
of each wire in question. If meter reads over
(equal to within
50 rpm), go to "ROUGH, 30,000
ohms, replace wire(s).
UNSTABLE, OR INCORRECT IDLE, - Fuel System - Plugged fuel filter, water, low
STALLING" symptom. Reconnect IAC pressure. See CHART A-7.
valve.
- Valve timing.
3. If there is no rpm drop on one or more - Secondary voltage using a shop ocilliscope or a
cylinders, or excessive variation in drop, spark tester 5-26792 (ST-125)
or equivalent.
check for spark on the suspected
@ Visually inspect distributor cap and rotor for
cylinder(s) with J 26792 (ST-125) Spark moisture, dust, cracks, burns, etc. Spray cap and
Gap Tool or equivalent. If no spark, see plug wires with fine water mist to check for
Section 6D for Intermittent Operation or shorts.
Miss. If there is spark, remove spark
@ A miss condition can be caused by EM1
plug(s) in these cylinders and check for: (Electromagnetic Interference) on the reference
- Cracks circuit. EM1 can usually be detected by
- Wear monitoring engine rpm with a "Scan" tool. A
- Improper Gap sudden
increase in rpm with little change in
- Burned Electrodes actual engine rpm change, indicates EM1 is
- Heavy Deposits present.
@ Perform compression check on questionable If
the problem exists, check routing of secondary
cylinder(s) found above. If compression is low, wires, check
all distributor ground circuits.
repair as necessary. See Section
"6". @ Remove rocker covers. Check for bent pushrods,
@ Disconnect all injector harness connectors. worn
rocker arms, broken valve springs, worn
Connect
5-34730-2 Injector Test Light or camshaft
lobes. Repair as necessary. See Section
equivalent 6 volt test light between the
"6A".
harness terms, of each injector connector and
note light while cranking. If test light fails to
BACKFIRE
Definition: Fuel ignites in intake manifold, or
in exhaust system, making a loud popping noise.
@ CHECK: - Spark plugs for crossfire also inspect (distributor
- Loose wiring connector or air duct at MAF
cap, spark plug wires, and proper routing of plug
sensor. wires).
- Compression - Look for sticking or leaking - Ignition system for intermittent condition. (See
valves. Section
"6D").
- EGR operation for being open all the time. See - Engine timing - see emission control information
CHART C-7. label.
- EGR gasket for faulty or loose fit. - Perform fuel system diagnosis check, CHART A-
- Valve timing. 7A.
- Output voltage of ignition coil using a shop - Perform injector balance test CI-IART C-2A.
ocilliscope or spark tester 5-26792 (ST-125) or
- A.I.R. system check valves - See Section "C-6".
equivalent.