1988 PONTIAC FIERO sensor

MULTI-PQRT FUEL INJECTION: V8 VIN 8
COMPONENT LOCATION Page-Figure
Manifold
Air amperatwe (MAT)
........... Sensor (VIN F) (VIN 8) Top of intake manifold
Mass
Air Flow (MAF) Relay (VIN F)
........................ (VIN 8) LH rear corner of engine compartment. on relay
bracket
.................................
Mass Air Flow (MAF) Sensor (VIN F)
........................ (VIN 8) Front of engine coqartment. on rear of air
.................................. cleaner
Oxygen Sensor (VIN F) (VIN 8) ..... Lower LW side of engine. on exhaust manifold
Throttle Position Sensor (VIN
F)
........................ (VIN 8)
Top center of engine ........................
....... ............. Vehicle Speed Sensor Buffer BeGnd RH side of IIP. near ECM
................ C100 (42 cavities) LH front of dash. left of brake master cylinder ..
6113 (1 cavity) (VIN F) (VIM 8) ..... Taped to engine harness. RH front of dash ......
C114 (1 cavity) (VIN F) (VIN 8) ..... Taped to engine harness. above rear of engine ...
C143 (1 cavity) (VIN F) (VIN 8) ..... Lower LH side of engine. below exhaust manifold
.......................................
.......................... ................. C172 (2 cavities)
Top rear of engine
................ C207 (15 cavities)
Behind RI-I side of IIP. near ECM .............
................. .................... C313 (3 cavities) Below center of back seat
............. GI12 (VIN F) (VIN 8)
Rear of LN cylinder head ....................
............. .................... 6118 (VIN F) (VIN 8) Rear of RH cylinder head
.......................... 6200
Behind IIP. left of steering column ............
.......................... 6304
Under rear seat. on support bracket
............. S142 (VIN F) (VIN 8)
Engine harness. behind RH side of IIP
............. ............. S143 (VIN F) (VIN 8) Engine harness. RH front of dash
............. S145 (VIN F) (VIN 8)
Engine harness. above LH rear of engine .......
............. S146 (VIN F) (VIN 8)
Engine harness. behind RH side of IIP
........................... S158
Engine harness. behind RN side of IIP
........................... S162 Engine harness. LK rear corner of engine
compartment
............................
........................... S164 I/P harness. above Fuse Block ................
............. S166 (VIN F) (VIN 8) Engine harness.
above LN rear of engine .......
............. ............. S168 (VIN F) (VIN 8) Engine harness. RH front
of dash
........................... ............. S171 Engine harness. RN front of dash
1 S172 (VIN F) (VIN 8) ............. ~n& harness. RH front of dash .............

COOLANT FAN I g
TROUBLESHOOTING HINTS
@ Try the following checks before doing the Sys-
tem Check.
1. Check the CIH-FAN Fuse if the Coolant Fan
does not run.
2. Check that ground 6112 (V6 VIN S), 6117
(V8 VIN E) or 6104 (V8 VIN F and V8 VIN
8) is clean and tight.
3. Check the Fusible Link (see schematic).
4.
If the Coolant Fan runs with the Ignition
Switch OFF, replace the Coolant Fan Relay.
@ Go to System Check for a guide to normal
operation.
Go to System Diagnosis for diagnostic tests.
SYSTEM CHECK
Use the System Checlc Table as a guide to
normal operation.
SYSTEM CHECK TABLE
I ACTION I NORMALRESULT 1
COMPONENT LOCATION Page-Figure
Assembly Line Diagnostic Link
(ALDL) Connector .............. On bottom of IIP hush panel, to right of steering
column
Auxiliary Coolant Fan Relay
....... RH front side of engine compartment. ......... 201- 5-A
Auxiliary Coolant Fan Switch
...... Lower RN rear of engine .................... 201- 6-A
Coolant Fan Relay (VIN
E). ........ LH rear corner of engine compartment, on relay
bracket
................................. 201- 3-A
Coolant Fan Relay (VIN F) (VIN 8)
. . Front of engine compartment, RN side of
radiator support.
......................... 201- 5-A
Coolant Fan Relay (VIN S)
......... LH rear corner of engine compartment, on relay
................................. bracket 201- 0-A
Coolant Fan Switch
.............. Lower RH rear of engine, above starter solenoid . 201- 4-A
Coolant Temperature Sensor (VIN F)
(VIN 8).
....................... Top LW front of engine. ..................... 201- 8-C
Coolant Temperature Sensor (VIN S) Top LH front of intake manifold.
............. 201- 0-A
Electronic Control Module (ECM)
... Behind RN side of IIP ...................... 201-12-B
Fan Pressure Switch (VIN F) (VIN 8) Lower RH side of engine, on
AIC line .......... 201- 5-A
Fan Pressure Switch (VIN S)
....... Lower RN front of engine compartment, on AIC
line .................................... 201- 1-A
Fuse Block.
..................... Behind LN side of IIP, below light switch. ...... 201-10-A
Fusible Link
N (VIN E) ........... RH front of engine compartment, at Junction
Block ................................... 201- 3-B
Fusible Link N (VIN F) (VIN 8).
.... LN front of engine compartment, behind battery 201- 5-C
Fusible Link
J (VIN S) ............ RN side of radiator support, at Junction Block .. 201- 1-A
Redundant Cooling Fan Switch.
.... Top RW rear of engine ...................... 201- 1-6
C102 (4 cavities) ................. Center front of dash. ....................... 201-14-A
6104 (6 cavities)
................. Front of engine compartment, RH side of
................................ radiator. 201- 5-A
C204 (4 cavities) ................. Above LH rear corner of engine .............. 201- 0-A
C207 (15 cavities)
................ Behind RH side of IIP, near ECM ............. ,201-13-A
C224 (6 cavities) ................. Center of IIP, behind AIC control ............. 201-14-B
6104
.......................... On radiator support, behind RN headlights. .... 201-16-A
6112 (VIN E)
................... Rear of LN cylinder head. ................... 201- 3-C
6112 (VIN S)
.................... Rear of LH cylinder head. ................... 201- 0-C
6118 (VIN F) (VIN 8)
............. Rear of RH cylinder head. ................... 201- 5-A
6118 (VIN S)
.................... Rear of RH cylinder head. ................... 201- 1-C
(Continued on next page)
With
the engine cold
and idling, turn the
AIC Selector to
NORM (if equipped
with Ale)
VIN E: Coolant Fan
turns on
VIN S, VIN
F &
VIN 8: Coolant Fan
(and Auxiliary
Coolant Fan-if
equipped) turns on
when
A/C Control
Head Pressure
exceeds 233 psi
(1600
kPa)
(Continued on next page)

COOLANT FAN I $
A: COOLANT FAN OPEN TEST (TABLE
3)
Connect: FUSED JUMPER
At: COOLANT FAN RELAY CONNECTOR
(Disconnected)
Jumper Correct Result For Diagnosis
Between
1. Leave fused jumper in place and go to
Table
4.
E (RED) & A
(BLKIRED)
A: COOLANT FAN OPEN TEST (TABLE
41
Connect: TEST LAMP
At: COOLANT FAN CONNECTOR
(Disconnected)
Condition:
Fused jumper in place from Table
3.
If the Coolant Fan runs, replace the
Coolant Fan Relay. Coolant
Fan
runs
-. -. See --
B: COOLANT FAN SWITCH TEST
Connect
Between
B (BLKtRED)
& Ground
B (BLKIRED)
& A (BLK)
Connect: FUSED JUlVlPER
At: COOLANT FAN SWITCH CONNECTOR
(Disconnected)
Condition: lgnition Switch: RUN
Jumper
Between Correct
Result For Diagnosis
Coolant Fan
Ground
runs
If the Coolant Fan runs replace the
Coolant Fan switch.
1. Check BLK (335) wire for an open (see
schematic).
6: AIC CONTROL HEAD TEST
If the results are correct, replace the
Coolant Fan.
1. Check BLKIRED (532) wire for an open.
2. Check BLK (150) wire for an open.
Correct Result
Test Lamp
lights
Test Lamp
lights
Connect: FUSED JUMPER
At:
A/C CONTROL HEAD CONNECTOR Cl
(Disconnected)
Condition:
lgnition Switch: RUN
For Diagnosis
See 1
See 2
Jumper
Between I Correct Result I For Diagnosis I
".' Ground
J (DK GRN) & Coolant Fan See N (BLK) runs
If the results are correct, replace the
AIC
Control Head.
1. Check DK GRNIWHT (335) and DK GRN
(535) wires for an open (see schematic).
2. Check BLK (150) wire for an open (see
schematic).
D: COOLANT FAN SHORT TEST
1. With the Ignition Switch in RUN, remove
the Coolant Fan Switch.
If the fan continues to
run, go to step 2.
If the fan turns off, replace the Coolant Fan
Switch.
2. Remove the CIH-FAN Fuse.
If the fan turns off, go to step 3.
If the fan continues to run, replace the
Coolant Fan Relay.
3. Disconnect the
AIC Control Head and recon-
nect CIH-FAN Fuse.
If the fan continues to run,
check the DK
GRNIWHT (335) and BLK (335) wires for a
short to ground.
If the fan turns off, replace the
AIC Control
Head.
CIRCUIT OPERATION
V6 VIN S, V8 VIN F and V8 VIN 8
The Coolant Fan is controlled by the Elec-
tronic Control Module (ECM). In the V6 VIN S,
the Coolant Fan is also controlled by the Redun-
dant Cooling Fan Switch. When the ECM
grounds the 335 circuit, the Coolant Fan Relay
is energized and battery voltage is applied to
the Coolant Fan.
If the ECM fails (V6 VIN S),
the Redundant Cooling Fan Switch will ground
the 335 circuit and energize the Coolant Fan
Relay. The ECM will ground the Coolant Fan
Relay when the Coolant Temperature Sensor
indicates the coolant temperature is greater
than 106
OC (222 OF) or when the AIC Control
Head pressure is greater than 233 psi (1600
kPa) and the vehicle speed is less than 40 mph.

VEHICLE SPEED SENSOR: PERMANENT MAGNET GENERATOR
ELECTRONIC
CONTROL
MODULE (ECM
SOLID STATE
DO NOT
MEASURE RESISTANCE CRUISE
- CONTROL
MODULE
SOLID SFATE DO NOT
MEASURE RESISTANCE

VEHICLE SPEED SENSOR
TROUBLESHOOTING HINTS
0 Try the following checks before doing the
System Diagnosis
.
1
. Check the Gages Fuse by observing the Brake
Indicator when applying the Parking Brake
wrth the Ignition Switch in RUN (engine not
running)
.
2 . Check ground 6118 .
3 . If only the Speedometer or only the Odometer
does not work. replace the suspect item
.
Go to System Diagnosis for diagnostic tests .
SYSTEM DlAGNOSlS
Do the tests listed for your symptom in the
Symptom Table below
.
Tests follow the Syrnptom Table .
COMPONENT LOCATION Page-Figure
Cruise Control Module
............ Behind RN side of IlP ...................... 201-11-A
Electronic Control Module (ECM)
... Behind RN side of IIP ...................... 201-12-B
Fuse Block
...................... Behind LN side of IIP. below light switch ....... 201-10-A
Vehicle Speed Sensor
............. Lower LEI rear of transmission ............... 201- 8-D
Vehicle Speed Sensor Buffer
....... Behind RH side of IIP. near ECM ............. 201-13-A
ClOO (42 cavities) ................ LN front of dash. left of brake master cylinder .. 201- 0-A
C207 (15 cavities) ................ Behind RH side of IIP. near ECM ............. 201-13-A
C209 (2 cavities)
................. Behind RN side of IIP. left of Cruise Control
................................. Module 201-11-A
6118 (VIN E)
................... Rear of RH cylinder head .................... 201- 5-B
6118 (VIN F) (VIN 8) ............. Rear of RN cylinder head .................... 201- 5-A
6118 (VIN S)
.................... Rear of RN cylinder head .................... 201- 1-C
S143 (VINE)
.................... Engine harness. RH front of dash ............. 201- 2-A
S143 (VIN F) (VIN
8) ............. Engine harness. RN front of dash ............. 201- 6-A
S143 (VIN S)
.................... Engine harness. center front of dash ........... 201- 1-A
S202
........................... IIP harness. behind RH side of IIP ............ 201-13-A
S204
........................... IIP harness. behind instrument cluster ......... 201-10-A
S217 ........................... IIP harness. behind center of IIP .............. 201-10-A
SYMPTOM TABLE
I SYMPTOM I FOR DIAGNOSIS I
=liter does not operate properly. ECM I Do Test B
code 24 is not set
ECM Code
24 is set. Speedometer is good
e If your symptom is not listed in the Symptom Table. pedorm all the tests .
Do Test C
See Section 6E of Service Manual
Speedometer does not operate properly. and ECM
Code
24 is set
Cruise Control does not operate properly. ECM
Code
24 is not set Do
Test
A
Do Test D

VEHICLE SPEED SENSOR
A: VEHICLE SPEED SENSOR BUFFER
TEST (TABLE
1)
At: VEHICLE SPEED SENSOR BUFFER CON-
NECTOR
62 (Disconnected)
Condition:
I e lnnition Switch: RUN I
I ztmz) I Battery I See 1 /
Measure
Between
A: VEHICLE SPEED SENSOR BUFFER
TEST (TABLE
2)
Measure: AC VOLTAGE
At: VEHICLE SPEED SENSOR BUFFER CON-
NECTOR Cl (Connected)
Conditions:
e Ignition Switch: RUN
e Gear Selector: NEUTRAL
e Turn drive wheels by hand while
making measurement
Measure
I Correct AC 1 For
Correct
Voltage
H (PNKJBLK)
& A (BLKJ
WNT)
B: INSTRUMENT CLUSTER INPUT TEST I
For
Diagnosis Measure:
VOLTAGE
At: VEHICLE SPEED SENSOR BUFFER
CONNECTOR C2 (Disconnected)
Condition: lgnition Switch: RUN
* If both voltages are correct, go to Table 2.
1. Checklrepair PNKJBLK (39) wire for an
open (see schematic).
2.
ChecWrepair BLKIWHT (450) wire for an
open (see schematic). Check that ground
6118 is clean and tight. Battery
See
2
Measure
Between Correct I For Diagnosis I I Voltage
Between
A (YEL) & C
(PPL)
( CgEg?' I Battery I See 1
e If the voltage is correct, replace the Vehicle
Speed Sensor Buffer.
1.
ChecWrepair the UEL (400) and PPL (401)
wires (see schematic). Replace Vehicle
Speed Sensor if both wires are OK, and
connector
C100 is correctly mated.
Voltage
1 volt AC to 5
volts
AC
Ground I
Vehicle Speed Sensor Buffer: CON-
NECTED
Gear Selector: NEUTRAL
Diagnosis
See
I 0 Turn drive wheels by hand while making I
measurement
I
If voltages are correct, repairlreplace
SpeedometerIInstrument Cluster.
1. Check LT GRNIBLK (537) wire for open
or short to ground. If OK,
repairireplace
Instrument Cluster after verifying power
inputs to Cluster (see Section
8A-81 or
82).
2. Replace Vehicle Speed Sensor Buffer.
(LT GRN1
BLK' &
Ground
Varying from
less than
5.
volt to more
than 4 volts See 2

VEHICLE SPEED SENSOR
C: ECM INPUT TEST
At: VEHICLE SPEED SENSOR BUFFER
CONNECTOR
62 (Disconnected)
Gear Selector: NEUTRAL
1. Check BRN and
BRNIYEL (437) wires for
an open or short to ground. Also check
that connections are good. If
OK, replace
1 2. Replace Vehicle Speed Sensor Buffer.
At: VEHICLE SPEED SENSOR BUFFER
CONNECTOR
C2 (Disconnected)
Gear Selector: NEUTRAL
nosis. If Section 8A-34 refers you back to
this section (Vehicle Speed Sensor,
8A-33), replace Cruise Control Module.
1. Check RED (381) wire for open or short to
ground. If wire is good, replace Cruise
Control Module.
D: CRUISE CONTROL lNPUT TEST CIRCUIT OPERATION
The Vehicle Speed Sensor (VSS) generates a
signal that indicates the speed of the vehicle.
This signal is processed by the solid state
Vehicle Speed Sensor Buffer to supply inputs to
the Electronic Control Module (ECM), the
Cruise Control Module
and the Speedometer.
The Vehicle Speed Sensor is mounted in the
Transmission.
A magnet rotates near a coil,
producing voltage pulses in the coil. The
frequency of the AC voltage coming from this
coil depends on the vehicle speed. As the speed
increases, so does the number of voltage pulses
per second.
The Vehicle Speed Sensor Buffer takes the
sensorlvoltage pulses from the sensor and uses
them to close three solid state output switches.
Each output terminal is switched to ground at a
rate that is proportional to the speed of the car.
The sensor generates 4000 pulses per mile
(ppm). The Speedometer is switched at
a
frequency of 4000 ppm. The ECM and the
Cruise Control use a lower frequency, 2000
pulses per mile. Their output pulses are
operated by a circuit after it has divided the
sensor frequency by two.

r--------------------------------------------------------------------------------------------------------------- I I IGNITION
I I I I SERVO I VACUUM I
I POSITION I
I SENSOR I INPUT I
CONNECTED
TO THROTTLE