1988 PONTIAC FIERO turn signal

6E3-C8-2 5.OL (VIN F) & 5.7L (VIN 8) DRIVEABILITY AND EMISSIONS
15-WAY I.P. CONNECTOR
VEHICLE SPEED SIGNAL
SPEED INPUT
4TH GEAR SIGNAL
422
TANIBLK
4TH GEAR SW.
TRANSMISSION ALDL CONNECTOR
TCC APPLY SOLENOID
CHART C-8A
(Page 1 of 2)
AUTOMATIC TRANSMISSION CONVERTER CLUTCH (TCC)
5.OL (VIN F) & 5.7L (VIN 8) "F'" SERIES (PORT)
Circuit Description:
The purpose of the automatic transmission torque converter clutch feature is to eliminate the power loss of
the torque converter stage when the vehicle is in a cruise condition. This allows the convenience
of the
automatic transmission and the fuel economy of
a manual transmission. The heart of the system is a solenoid
located inside the automatic transmission which is controlled by the ECM.
When the solenoid coil is activated
("ON"), the torque converter clutch is applied which results in straight
through mechanical coupling from the engine to transmission. When the transmission solenoid is deactivated,
the torque converter clutch is released, which allows the torque converter to operate in the conventional manner
(fluidic coupling between engine
and transmission).
The ECM turns "ON" the TCC when coolant temperature is above
65" C (149" F), TPS not changing ,and
vehicle speed above
a specified value.
Test Description: Numbers below refer to circled Diagnostic Aids:
nbers on the diagnostic chart.
When
a test light is connected from ALDL
terminal "F" to ground, a test light "ON" indicates
battery voltage is
OK and the TCC solenoid is
disengaged.
When the diagnostic terminal is grounded, the
ECM should energize the TCC solenoid and the
test light should go out.
A "Scan" tool only indicates when the ECM has
turned "ON" the TCC driver (grounded CKT
422) but
this does not confirm that the TCC has engaged. To
determine if TCC is functioning properly, engine rpm
should decrease when the "Scan" indicates the TCC
driver has turned "ON". To determine if the 4th gear
switch is functioning properly, perform the checks in
CHAW C-8A (Page 2 of 2). The switches will not
prevent TCC
from functioning but will affect TCC lock
and unlock points. If the 4th gear switch circuit is
always open, the TCC may engage as soon as
si~t'ficient oil pressure is reached.

6E3-C8-4 5.OL (\/IN F) & 5.7b (VIN 8) DRIVEABILITY AND EMISSIONS
15-WAY I.P. CONNECTOR
SPEED INPUT
4TH GEAR SIGNAL
4TH GEAR SW.
TRANSMISSION
ALDL CONNECTOR
APPLY SOLENOID
CHART C-8A
(Page 2 of 2)
TRANSMISSION CONVERTER CLUTCH (TCC) ELECTRICAL DIAGNOSIS
5.OL (VIN F) & 5.7L (VIN 8) "F" XRlES (PORT)
Circuit Description:
A 4th gear switch (mounted in the trans.) opens when the trans. shifts into 4th gear, and this switch is used
by the ECM to modify TCC lock and unlock points, when in a 4-3 downshift maneuver.
Test Description: Numbers below refer to circled
numbers on the diagnostic chart.
1. Unless the switch or CKT 446 is open, the "Scan"
should display "NOJ', indicating the trans. is not
in 4th gear. The 4th gear switch should only he
open while in 4th gear.
2. This step determines if the ECM and wiring are
OK. Grounding CKT 446 should cause the "Scan"
to display "NO", indicating the trans. is not in 4th
gear.
3. Checks the operation of the 4th gear switch.
When the trans, shifts into 4th gear the switch
should open and the "Scan" should display "YES".
4. Disconnecting the TCC connector sin~ulates an
open switch to determine if CKT 446 is shorted to
ground or the problem is in the transmission.
Diagnostic Aids:
A road test may be necessary to verify the
customer complaint.
If the "Scan" indicates TCC is
turning
"ON" and "OFF" erratically, check the state
of the 4th gear switch to be sure it is not changing
states under a steady throttle position. If the switch is
changing states, check connections and wire routing
carefully. Also, if the 4th gear switch is always open
the
'l'CC may engage as soon as sufficient oil pressure
is reached.

DRlVEABlLlPV AND EMISSIONS 5.OL (VIN F) & 5.7L (VIN 8) 6E3-C"1-1
SECTION Cl2
COOLING FAN CONTROL
CONTENTS
GENERAL DESCRIPTION ................ C12-I DIAGNOSIS ......................... C1Z-1
OPERATION ..................... .. C12-1 ON-CARSERVICE ..................... C12-1
PARTS INFORMATION ................. C12-1
GENERAL DESCRIPIION DlAGNODlS
The fan is used for engine and AIC condenser
cooling but the fan only operates under certain
conditions. The
following charts will diagnose the ECM
controlled cooling fan.
Use
Sect.ion "8A" to diagnose the secondary
cooling fan.
OPERATION
ON-CAR SERVICE
The electric cooling fan on this engine is controlled
by the ECM. The ECM will ground the cooling fan
relay, which turns "ON" the fan, when the following
conditions are met.
@ Coolant temperature sensor signal indicating a
temperature greater than 106°C
(222°F).
@ AIC head pressure greater than 233 psi and
vehicle speed less than 40 mph.
When the cooling fan is turned "ON", it will stay
"ON" for a minimum time of 15 seconds. Cooling
system component replacement can be
found in Section
"6B".
PARTS INFORMATION
PART NAME GROUP
......................... Fan, Engine 1.055
......................... Motor, Fan. 1.055
.................... Relay, Engine Fan 1.055

6E3-C12-2 5.OL (VIN F) & 5.7b (VIN 8) DRIVEABILITY AND EMISSIONS
FAN CONTROL
RELAY CONN.
DK GRNNVHT 335
TEMPERATURE
SENSOR SIGNAL.
TURNS ON PRIMARY
FAN AT
223OF (1 06'C)
CHART C-12
(Page 1 of 2)
COOLING FAN CONTROL CIRCUIT
5.8L (VIN F) & 5.7L (VIN 8) "F" SSERlES (PORT)
Circuit Description:
The primary cooling fan is totally controlled by the ECM based on inputs from the coolant sensor and
fan control switch. The fan should run, if coolant temperature is greater than 106°C
(223°F).
@ Battery voltage is supplied to the fan relay on terminal "En and ignition voltage to terminal "D".
@ Grounding CKT 335 (relay terminal "F") will energize the relay and supply battery voltage to the fan
motor. Once the fan relay is energized by the
ECM, it will remain "ON" for a minimum of 15 seconds.
@ 'I'he ECM will remove the ground to CKT 335 if vehicle speed is over 40 rnph unless the engine is
overheating.
@ 'I'he fan control switch, mounted in Lhe AIC high pressure line, will close when head pressure exceeds
233 psi (1600 kPa) and this input causes the ECM to ground CKT 335.
@ If a Code 14 or 15 sets, or if the ECM is operating in the fuel back-up mode, the ECM will turn "ON"
the cooling fan.
Diagnostic Aids:
If the owner complained of an overheating If
the engine is actually overheating and the gage
problem, it must be determined if the complaint was indicates
overheating, but
t,he cooling fan is not
due to an actual boil over or the hot light or coming
"ON", the
coolant sensor has probably shifted
temperature gage indicated overheating. out
of calibration and should be replaced.
If the gate or light indicates overheating, but no If
the engine is overheating, and the cooling fan is
boilover is detected, the gage circuit should be "ON", the cooling system should be checked.
checked. The gage accuracy can also be checked by
comparing the coolant sensor reading using
a "Scan.'
tool and comparing its reading with the gage reading.

6E3-C12-4 5.8L (VIN F) & 5.7L (VIN 8) DRIVEABILITY AND EMISSIONS
FAN CONTROL
SINGLE PIGTAIL RELAY CONN.
DK GRNNVHT 335
OPENS AT
185 TEMPERATURE SENSOR SIGNAL.
TURNS ON PRIMARY
FAN AT 223°F
(106°C)
CHART C-12
(Page 2 of 2)
COOLING FAN CONTROL CIRCUIT
5.OL (VIN F) & 5.7L (VIN 8) ""FYSERlES (PORT)
Circuit Description:
@ The primary cooling fan is totally controlled by the ECM based on inputs from the coolant sensor and
fan control switch. The fan should run, if coolant temperature is greater than 106°C
(223°F).
@ Battery voltage is supplied to the fan relay on terminal "En and ignition voltage to terminal "I)"
@ Grounding CKT 335 (relay terminal "F") will energize the relay and supply battery voltage to the fan
motor. Once the fan relay is energized by the ECM, it will remain "ON" for a mini~nuln of 15 seconds
@ The ECM will remove the ground to CKT 335 if vehicle speed is over 40 mph unless the engine is
overheating.
@ The fan control switch, mounted in the A/C high pressure line, will close when head pressure exceeds
233 psi (1600 kPa) and this input causes the ECM to ground CKT 335.
@ If a Code 14 or 15 sets, or if the ECM is operating in the fuel back-up mode, the ECM will turn "OX"
the cooling fan.
Diagnostic Aids:
If the owner complained of an overheating If the engine is actually overheating and the gage
problem, it must be determined if the complaint was indicates overheating, but the cooling fan is not
due to an actual boil over or the hot light or coming
"ON", the coolant sensor has probably shifted
temperature gage indicated overheating. out
of calibration and should be replaced.
If the gate or light indicates overheating, but no If the engine is overheating, and the cooling fan is
boilover is detected, the gage circuit should be "ON". the cooling system should be checked.
checked. The gage accuracy can also be checked
by
comparing the coolant sensor reading using a "Scan"
tool and comparing its reading with the gage reading.

DRIVEABILITY AND EMISSIONS - FUEL INJECTION 6E-9
ParWNelatral Switch IAC (Idle Air Control)
The indication in this mode may vary with This system is used to control engine idle speed to
manufacturer so the type of reading for a particular the desired rpm, for different operating conditions. In
tool should be checked in the operator's manual. The this mode, the numbers will indicate the position to
important thing is that the the reading changes state which
the ECM has moved the valve pintle. The ECM
(switches) when the gear selector is moved from moves
the IAC in counts, or steps, and the number of
paridneutral to drive or reverse. these counts are displayed on a "Scan" tool.
"Trque Convertor Clutch (TCC)
In this position, the tool will indicate when the
TCC has been commanded by the ECM to turn "ONJ'.
This does not necessarily mean that the clutch was
engaged but only that the
ECM grounded the circuit
internally. The best way to determine if the clutch has
engaged is to monitor engine rpm when the TCC
comes "ON".
EGR (Duty Cycle)
The EGR system uses a valve to feed a small
amount of exhaust gas back into the intake manifold
to control formation of NO,. Like all ECM outputs, the
"Scan" tool only indicates that the ECM has
commanded the function, and does not indicate that
the function has really happened.
EGR Position
This indicates the position of the EGR pintle.
Integrator and Block Learn
Normal readings for these positions are around
128. If higher, it indicates that the ECM is adding fuel
to the base fuel calculation because the system is lean,
and if the numbers are below 128, the ECM is taking
out fuel from the base calculation because the system
is rich. The integrator gives short term corrective
action, while the block learn portion (which is a long
term correction) will only change if the integrator has
seen a condition which lasts for a calibrated period of
time.
Block Learn Multiplier (BLM) Cell - or -
Block Learn Memory (BLM)
There are up to sixteen different cells,
corresponding to ranges of rpm and engine load
(indicated by MAF or MAP signals), and other
conditions, such as
A/C or P/N switch "ON" or "OFF",
etc. The ECM learns how much adjustment is needed
in each cell, and retains it in memory, so that the
adjustment will immediately be made when the
engine operates in that cell (or
rpmlload range). This
parameter will display what cell the ECM is currently
using for the fuel calculation.
Desired RPM
This indicates the rpm to which the ECM is trying
to control the idle.
Shift Light
This displays "yes" when the ECM is commanding
the shift light to turn "ON".
PPSW (Pump Prime Switch)
This is the voltage on the fuel pump feed circuit.
The ECM will adjust fuel injector base pulse width
from this voltage value rather than from battery
voltage.
NC Request
The state of the A/C signal line to the ECM is
shown. It should read "yes" whenever the
IVC is
requested.
NC Clutch
"ON" is displayed when the ECM has commanded
the
A/C clutch "ON".
Knock Retard
This indicates the number of degrees the ECM is
retarding the electronic spark timing (EST).
Knock Signal
This displays a "yes" when knock is detected by
the ECM, and a "no" when knock is not detected.
Battery Voltage
This displays the battery voltage detected at the
ECM ignition input.
Fan
"ON" is displayed when the cooling fan has been
commanded "ON".

DRIVEABILITY AND EMISSIONS - FUEL INJEC"F0N 6E-11
@ A/% "On" or "Off" r Air Management
r Engine Coolant Temwrature r Canister Purge
@ Engine crank signal r Exhaust Gas Recirculation (EGR)
@ Exhaust Oxygen(02) Sensor @ Electronic Spark Timing (EST)
r Distributor Reference @ Fuel Control
@ Crankshaft Position @ Idle Air Control (lAC)
@ Engine Speed (RPM) Transmission Converter Clutch (TCC)
Manifold Absolute Pressure (MAP)
@ Park Neutral Switch (PB) Position @ Electric Fuel Pump
r System Voltage Air Conditioning
r Throttle Position (TPS) @ Engine Cooling Fan
r Transmission Gear Position
r Vehicle Speed (VSS) @ "Service Engine Soon" Light
@ Fuel Pump Voltage @ Diagnostic Terminal (ALDL)
r Power Steering Pressure @ Data Output (ALDL)
Mass Air Flow (MAF) @ Electronic Spark Control (ESC)
@ Manifold Air Temperature (MAT) @ Early Fuel Evaporation (EFE)
r EGR Vacuum @ Idle Speed (ISC, ILC,)
@ Engine Knock (ESC)
r Differential Pressure (VAC) 6-1-87
*7S
3429- 6E
Figure
4 - ECM Operating Conditions Sensed and Systems Controlled
driveaway. This system is not used on all engines and Electric Cooling Fan Control
may or may not be controlled by the ECM.
Under certain conditions, the
ECM may control
Exhaust Gas Recirculation (ECR) the electric cooling fan to cool the engine and A/C
condenser. At cruising speed, the ECM may turn the
The
EGR system uses a valve to feed a small fan
off for better fuel economy. This control is on
amount of exhaust gas back into the intake manifold transverse
engine front wheel drive vehicles.
to control formation of
NO,.
Positive Crankcase Ventilation (PCV) or
Transmission Converter
Clutch (TCC) Crankcase Ventilation (CV)
The TCC is ECM controlled and is used on all
engines with an automatic transmission. This system
reduces slippage losses in the torque converter by
coupling the engine flywheel to the output shaft of the
transmission.
Shift Light Control
The ECM controls the shift light on some manual
transmission vehicles to indicate the best shift point
for maximum fuel economy. This control is not on all
applications.
NC Clutch Control
The ECM may control the AJC clutch on the
compressor to improve idle quality. This control is not
on all engines. The
PCV or CV system passes crankcase vapors
into the intake manifold. This system is not controlled
by the
ECM and is used on all engines.
Thermostatic Air Cleaner (THERMAC)
The THERMAC system regulates heated air
through the air cleaner to provide uniform inlet air
temperature, which gives good driveability under
various climatic conditions. This system is not
controlled by the
ECM.
ABBREVIATIONS AND GLOSSARY OF TERMS
Abbreviations used in this section are listed below
in alphabetical order with an explanation of the
abbreviation. There are some variations in the use of
periods and in capitalization (as mph,
m.p.h., Mph,

6E-14 DRIVEABILITY AND EMISSIONS - FUEL INJECTION
N.O. - NORMALLY OPEN - State of relay contacts
or solenoid plunger when no voltage
is applied.
NOx - NITROGEN, OXIDES OF - One of the
pollutants found in engine exhaust.
O2 - OXYGEN (Sensor) - Monitors the oxygen
content of the exhaust system and generates a voltage
signal to the ECM.
OIL or OILOOP - OPEN LOOP - Describes ECM fuel
control without use of oxygen sensor information.
OUTPUT - Result of a function typically controlled
by the ECM.
OXYGEN SENSOR. EXHAUST - Device that detects
the amount of oxygen
(02) in the exhaust stream.
P.A.1.R - PULSE AIR INJECTION REACTOR system -
pulsed air directed into engine to reduce exhaust
emissions.
PCV - POSITIVE CRANKCASE VENTILATION -
Prevent fumes in crankcase from passing into
atmosphere.
PFI - PORT FUEL INJECTION
PIN
- PARWNEUTWL
PORT - EXHAUST OR INTAKE PORT
PROM
- PROGRAMABLE READ ONLY MEMORY-
an electronic term used to describe the engine
calibration unit
.
RPM - REVOLUTIONS PER MINUTE - A measure of
rotational speed.
RVB - REAR VACUUM BMKE - is used to control
choke operation during cold engine conditions.
SELF-DIAGNOSTIC CODE - The ECM can detect
malfunctions in the system.
If a malfunction occurs,
the ECM turns on the "Service Engine Soon" light.
A
diagnostic code can be obtained from the ECM
through the "Service Engine Soon" light, or by use of a
"Scan" tool. This code will indicate the area of the
malfunction.
SES - SERVICE ENGINE SOON LIGHT - Lights when
a malfunction occurs in Computer Command Control
system.
TACH - TACHOMETER
TBI
- THROTTLE BODY INJECTION (Unit) - is
controlled by the ECM to supply precise airlfuel
mixture into the intake manifold.
TCC - TWNSMISSION I TRANSAXLE CONVERTER
CLUTCH
- ECM controlled solenoid in transmission
which positively couples the transmission to the
engine.
THERMAC - THERMOSTATIC AIR CLEANER -
provides preheated air to intake manifold to provide
better driveability when engine
is cold.
TPS - THROnLE POSITION SENSOR - Device that
tells the ECM the throttle position.
TVS - THERMAL VACUUM SWITCH - Used to
control vacuum in relationship to engine temperature.
V - VOLT
V-6 - SIX CYLINDER ENGINE - Two banks of
cylinders, arranged in a
"V".
V-8 - EIGHT CYLINDER ENGINE - Two banks of
cylinders, arranged in a
"V".
VACUUM - Negative pressure; less than
atmospheric pressure.
VACUUM, MANIFOLD - Vacuum source in
manifold below throttle plate.
VACUUM, PORTED - A vacuum source above I (atmospheric side ) of closed throttle plate. , I
WAC SENSOR - Abbreviation for differential
pressure sensor which is a
vacuum sensor.
VIN - VEHICLE IDENTIFIUTION NUMBER. 1
VSS - VEHICLE SPEED SENSOR - Sensor which
sends vehicle speed information to the ECM.
WASTECATE - A means of controlling the amount
of boost available for a Turbo charged engine.
WOT- WIDE OPEN THROPTLE. I
WIRING HARNESS SERVICE I
The ECM wire harness electrically connects the
ECM to the various solenoids, switches, and sensors in
vehicle engine compartment. The ECM is located
inside the vehicle passenger compartment.
Most connectors in the engine compartment are
protected against moisture and dirt which could create
oxidation and deposits on the terminals. This
protection is important because of the very low voltage
and current levels found in the electronic system. The
connectors have a lock which secures the male and
female terminals together. A secondary lock holds the
seal and terminal into the connector.
GENERAL
Molded-on connectors (like Metri-Pack) require
complete replacement of the connector. This means
splicing a new connector assembly into the harness.