1988 PONTIAC FIERO check engine

INSTRUMENT PANEL: GAGES CLUSTER
TROUBLESHOOTING HINTS COMPONENT LOCATION Page-Figure
* For a list of possible symptoms, go to System Coolant Temperature Sender (VIN E) Lower LH side of engine ....................
Diangosis. Coolant Temperature Sender (VIN F)
....................... .................... * For Instrument Cluster removal and replace- (VIN 8). Lower
LH side of engine
ment procedures, see Section 8C of the Ser- Coolant Temperature Sender (VIN S) Top LN front of engine, behind A/C Compressor.
.................. ..................... vice Manual. Fuel Tank Unit Top center of fuel tank.
..................... ...... * Try the following checks before doing the Sys- Fuse Block. Behind
LH side of IIP, below light switch.
................. tem Check. Ignition Switch. Behind IIP, on
top side of steering co
....... ........... Oil Pressure Sender (VIN E) Top rear of engine, near distributor. 1. Check GAGES Fuse by observing the . ........... Oil Pressure Sender (VIN F) (VIN 8) Top
rear of engine, near distributor.
BRAKE Warning Indicator with the Igni- Oil Pressure Sender (VIN S) ........ Lower LN side of engine .................... tion Switch in RUN and the Park Brake ................ .. el00 (42 cavities) LN
front of dash, left of brake master cylinder
applied.
................. C313 (3 cavities) Below
center of back seat. ...................
2. Check ground 6200. . 6118 (VIN F) (VIN 8) ............. Rear of RN cylinder head. ...................
.................... ................... 3. Check case ground of Coolant Temperature 6118
(VIN S) Rear
of RH cylinder head.
.......................... ............ Sender. 6200 Behind I/P, left of steering column ' h .......................... 4. Check case ground of Oil Pressure Sender. 6304 Under rear seat,
on support bracket
.......................... S204. IIP harness, behind instrument cluster. ........ 5. Check Indicator bulbs. .......................... ........ S205. I/P harness, behind instrument cluster. * Go to System Check for a guide to normal .......................... S217. I/P harness, behind center of IIP .............. operation.
* Go to Systern Diagnosis for diagnostic tests.
SYSTEM CHECK
* Use the System Check Table as a guide to
normal operation. Refer to the diagnosis given
if other results occur.
* Tests follow in System Diagnosis.

SYSTEM CHECK TABLE
FASTEN BELTS Indicator
lights for
6 to 8 seconds
See
Symptom Table
Oil Pressure Gage indicates
See
Syqtom Table
Coolant Temperature Gage
Voltmeter indicates Battery
Oil Pressure Gage indicates
See Symptom Table
engine oil pressure
L
Go to System Diagnosis for a list of symp-
toms.
SYSTEM DIAGNOSIS
Do the tests listed for your symptom in the
Symptom Table below, or when directed
by
the System Check.
r For Instrument Cluster removal and replace-
ment procedures, see Section
8C of the Ser-
vice
Manual.
Tests follow the Symptom Table.
SYMPTOM TABLE
I SYMPTOM 1 IFORDlAGMOSlS I
Fuel Gage indicates
EMPTY when there
is fuel in the tank
Fuel Gage indicates
FULL or beyond at
all times Do
Test
C: (Also see
Test
B terrnind PO)
Do Test D: (Nso see
Test
B terIllinal PO)
Fuel Gage is
inaccurate
Coolant
Temperature Gage
indicates NOT with
engine coolant cool
and Ignition Switch
in RUN Do
Test E: (Also see
Do Test F (Also see
Test B terminal
2)
coolant
Temperature Gage
indicates COLD at
all times Do
Test
6: (Also see
Test
B terminal 2)
Coolant Do Test N: (Also see
Temperature Gage
Test
B terminal 2)
is inaccurate
(Continued on next page)

INSTRUMENT PANEL: GAGES CLUSTER
I Oil Pressure Gage
(Continued from previous page)
indicates low
pressure
and oil
pressure is good
Coolant
Temperature Gage
does not indicate
HOT with Ignition
Switch in START or
BULB TEST, but
does operate
accurately
Do Test I: (Also see
Test A
terminal B)
Check DK GRN (35)
wire and Ignition
Switch for opens
Repairlreplace as
necessary
Oil Pressure Gage
indicates high
pressure at
all times
and oil pressure is
good Do
Test
J: (Also see
Test A terminal
8)
Oil Pressure Gage is
inaccurate Do
Test K: (also see
Test A terminal
8)
Do Test L
Tachometer does not
operate
Speedometer1
Odometer is
inaccurate Do
Test M
Do Test N: (with
5-33431-873 harness
connector available)
One or both
Odometers do not
operate properly,
but Speedometer
operates accurately
I
Check the
Instrument Cluster
Printed Circuit for
cracks or flaws
Replace the
Speedometer1
Odometer Assembly
(Continued in next column) (Continued from previous
column)
Hi Beam Indicator
does not operate
properly See
Exterior lights
Section 8A-110
(Also see Test
B
terminal 8)
I operate properly
I
(Also see Test A
I
Seatbelt Indicator
and alarm do not
BRAKE Warning Indicator does not
work properly
I
See Warnings and
Alarms (see Index)
SERVICE
ENGINE SOON
Indicator does not
does not work See
Brake Warning
System, Section
8A-41 (Also, see
Test A terminal
1)
See Section 6E of
1 Service Manual
Do Test O
r
(Also, see Test B
terminals 7 and
9)

(Continued from previous page)
If the Speedometer reads correctly, refer to
Vehicle Speed Sensor, Section
8A-33 for fur-
ther diagnosis.
If the Speedometer reads incorrectly, check
LT GRN (537) wire and the Instrument Clus-
ter Printed Circuit for opens. Replace the
Speedometer Assembly if the wire and
Printed Circuit are good (see Section
8C).
O: UPSHIFT INDICATOR WIRE TEST
Disconnect ECM connector C207. Put the Igni-
tion Switch in RUN and measure the voltage at
terminal
H (see section 8A-21 or 22).
If battery voltage is present, see section
6E
for ECM diagnosis.
If battery voltage is not present, check the
TANIBLK (422) wire for an open or short to
Ground.
CIRCUIT OPERATION
The operation of an indicator is explained in
the operation of the circuit it is apart of. See the
circuit referred to for a complete description of
that indicator and the other components that
work with it. Only the gages and indicators that
do not appear in other schematics are described
in this section.
Tachometer
The Tachometer displays engine speed in
rpm. Voltage pulses are taken from the Ignition
System and sent to the Tachometer. Solid State
circuits process these pulses into a signal that
drives the pointer of the meter. The Tachometer
responds to the frequency of the voltage pulses.
These pulses increase with engine speed.
Fuel Gage
The pointer of the Fuel Gage is moved by the
magnetic field of two coils. The coils are at right
angles to each other. Battery voltage is applied
to the E coil and the circuit divides at the
opposite end of this coil. One path continues to
ground through the F coil. Another goes to
ground through the variable resistor of the Fuel
Gage Sender Unit.
When the tank is low, the resistance of the
Fuel Gage Sender is low. A large flow of current
passes through the E coil and the Fuel Gage
Sender resistor. This moves the pointer
towards E on the scale. When the tank is
full,
the sender resistance is high. More current
flows through the F coil, moving the pointer
toward F on the scale.
With two coils operating the pointer, the Fuel
Gage is not affected by changes in the voltage
of the system.
011 Pressure Gage
The engine oil pressure is displayed by the Oil
Pressure Gage. The pointer of the gage is
moved by two coils, and its operation is similar
to that of the Fuel Gage. The
Oil Pressure Sender is connected to the
junction of the two coils.
It has low resistance
when the oil pressure is low, and 90 ohms
resistance when the oil pressure is high. This
changing resistance changes the current flow
through the coils. The magnetic fields of the
coils move the pointer to indicate high or low
coolant temperature.
Voltmeter
The Voltmeter measures the electrical sys-
tem voltage with the Ignition Switch in RUN,
BULB TEST, or START. With the engine
stopped, the Voltmeter indicates battery condi-
tion. With the engine
running, the Voltmeter
indicates Charging System operation.
Coolant Temperature Gage
The Coolant Temperature Gage is also oper-
ated by two coils. Battery voltage is applied to
both coils. One is grounded directly
and the
other is grounded through the Coolant Tem-
perature Sender. This has 54 ohms resistance at
260
OF, 130 "C (hot coolant) and its resistance
becomes greater at lower temperatures. It is
appr~ximately 1284 ohms at 100 OF (40 '6). This
causes the current through the sender and one
coil to vary as the coolant temperature charges
and this moves the pointer.

INSTRUMENT PANEL: DIGITAL CLUSTER a
TROUBLESHOOTING HINTS COMPONENT LOCATION u Page-Figure
0 For a list of symptoms and their diagnosis. go
to System Diagnosis
.
0 For Instrument Cluster removal and replace-
ment procedures see Section
86 of the Ser-
vice Manual
.
* Try the following checks before doing the
System Check
.
1 . Check the CLSTR Fuse .
2 . Check the CTSY Fuse .
3 . Check the TAIL Fuse .
Coolant Temperature Sender (VIN E) Lower LH side of engine ....................
Coolant Temperature Sender (VIN F)
(VIN 8)
........................ Lower LH side of engine ....................
Fuel Tank Unit .................. Top center of fuel tank ......................
Fuse Block ...................... Behind LH side of IIP. below light switch .......
Ignition Coil (VIN E) ............. Top center rear of engine ....................
Ignition Coil (VIN F)(VIN 8) ....... RH rear side of engine ......................
Ignition Switch .................. Behind IIP. on top side of steering column ......
Oil Pressure Sender (VIN E) ....... Top rear of engine. near distributor ............
Oil Pressure Sender (VIN F) (VIN 8) . Top rear of engine. near distributor ............
Oil Pressure Sender (VIN S) ........ Lower LH side of engine ....................
................ .. 4 . Check the GAGES Fuse . el00 (42 cavities) LH
front of dash. left of brake master cylinder 201- 0-A
C114
(1 cavity) (VIN E) ............ Taped to engine harness. above rear of engine
5 . If more than one indicator is out. check the C114 (1 cavity) (VIN F) (VIN 8) ..... Taped to engine harness. above rear of engine ... 201- 7-B
battery voltage inputs . . C207 (15 cavities) ................ Behind RH side of IIP near ECM ............. 201-13-A
................. .................... * Go to System Check for a guide to C313 (3 cavities) Below
center of back seat 201- 9-C operation . 6118 (VIN F) (VIN 8) ............. Rear of RH cylinder head .................... 201- 5-A
0 Go to System Diagnosis for diagnostic tests . 6200 .......................... Behind IIP. left of steering column ............ 201-10-A
6304
.......................... Under rear seat. on support bracket
SYSTEM CHECK S143 (VIN F) (VIN 8) ............. Engine harness. RH front of dash ............. 201- 6-A
0 Use the System Check able as a guide to S201 ........................... IIP harness. behind instrument cluster ......... 201-10-A
normal operation . Refer to the diagnosis S203 ........................... I/P harness. behind instrument cluster ......... 201-10-A
........................... ......... given if other results occur . S204 IIP harness. behind instrument cluster 201-10-A
........................... ......... Tests follow in System Diagnosis . S205 IIP harness. behind instrument cluster 201-10-A
S217 ........................... IIP harness. behind center of IIP .............. 201-10-A
S225 ........................... IIP harness. behind instrument cluster ......... 201-10-A
(Continued on next page)

DRIVER INFORMATION CENTER (DDC) I $
TROUBLESHOOTING HINTS
@ Try the following checks before doing the
System Check.
1. Check GAGES Fuse by observing that the
Instrument Panel Lights come on with the
Headlight Switch in Park.
2. Check CLSTR Fuse by observing that the
Instrument Cluster operates
normally.
3. Cheek CTSU Fuse by observing that the
Courtesy Lights operate normally.
4. Check the TAIL Fuse by observing that the
Tail Lights operate normally.
5. Check that grounds 6200 and 6210 are
clean and tight.
@ Go to System Check for a guide to norrnal
operation.
@ Go to System Diagnosis for diagnostic tests.
SYSTEM CHECK
@ Use the System Check Table as a guide to
normal operation. Refer to the diagnosis given
if other results occur.
Tests follow in System Diagnosis.
COMPONENT LOCATION Page-Figure
Door Ajar Switch
................ On each center lock pillar
..................... Fuse Block.
Behind LH side of IIP, below light switch. ...... 201-10-A
Hatch Ajar Switch
............... Center of end panel, in cargo compartment
Lights Monitoring Module.
........ Behind IIP, at base of steering column
..................... Low Coolant Probe (Except VIN S) .. On RR rear of radiator. 201- 2-B
..................... Low Coolant Probe (VIN S) ........ On LR side of radiator. 201- 2-C
.............. Washer Fluid Level Switch ........ LN side of engine compartment 201-16-A
................ el00 (42
cavities) LN
front of dash, left of brake master cylinder .. 201- 0-A
................. 6216 (3 cavities) Behind LN side
of IIP, left of steering column
.................. C319 (1 cavity). Behind I/P, at
LN shroud
............. 6103 (Except VIN E) On radiator support, behind LH headlights. .... 201-16-A
.......................... ............ 6200 Behind IIP, left of steering column 201-10-A
.......................... 6210 Behind center of IIP, on support bracket ....... 201-10-A
.......................... 6215 Behind
LH side of IIP, left of steering column
.......................... .... S107. Front lights harness, behind LN headlights. 201-16-A
.......................... S201. IIP harness, behind instrument cluster. ........ 201-10-A
.......................... S203. I/P harness, behind instrument cluster. ........ 201-10-A
.......................... S204. I/P harness, behind instrument cluster. ........ 201-10-A
.......................... S205. I/P harness, behind instrument cluster. ........ 201-10-A
.......................... S245. Ajar harness, behind LN side of IIP
(Continued on next page)

DRIVER INFORMATION CENTER (DIC)
(Continued from facing page)
@ If both tests are good, replace the Washer
Fluid Level Switch.
1. Check the BLKIWHT (99) wire for an
open (see schematic).
2. Check the BLK (152) wire for an open (see
schematic).
6: WASHER FLUID LEVEL SHORTED
SwlTen TEST
Disconnect the Washer Fluid Level Switch Con-
nector
terminal A. Switch the Ignition to RUN
and observe the Low Washer Fluid Indicator
segment on windshield of the vehicle symbol on
the
me.
If the Low Washer Fluid segment is now off,
and Low Washer Fluid is not displayed,
replace the Washer Fluid Level Switch.
If the Low Washer Fluid segment lights, and
LOW
VirASHER FLUID is displayed, check
the
BLKIWWT (99) wire for a short to
ground.
B: LOW COOLANT PROBE CONNEC-
TOR TEST
If the Low Coolant message does not come on
and the indicator segment on the vehicle sym-
bol does not light with the coolant low, remove
the connector to the Low Coolant Probe. With
the Ignition in RUN the indicator
should oper-
ate after approximately
11 seconds.
If it does,
install a new Low Coolant Probe.
* If it does not, check YELIBLM wire to the
DIC Display for a short to ground. Install a
new DIC display if the wire is good.
E: LOW COOLANT PROBE RESISTANCE
TEST
If the LOW COOLANT message comes on and
the indicator segment on the vehicle symbol
lights with the engine coolant full, check the
resistance of the Low Coolant Probe and its
wire. Remove the connector from the probe and
measure the resistance to ground of the probe.
If the resistance is higher than 30,000 ohms,
instdl a new Low Coolant Probe.
If the probe
and its wiring are good, and the
display does not indicate properly, install a
new DIC.
F: HATCH AJAR SHORTED SWITCH
TEST
Disconnect the Hatch Ajar Switch Connector.
Switch the Ignition to RUN and observe the
Hatch Ajar Indicator segment on the trunk of
the vehicle symbol on the DIC.
If the Hatch Ajar segment is now off and
HATCH AJAR is not displayed, replace the
Hatch Ajar Switch.
o If the Hatch Ajar segment is still on, and
HATCH AJAR is displayed, check the
BLKl
ORN (158) wire for a short to ground (see
schematic).
6: WATCH AJAR OPEN SWITCH TEST
R SWITCH CONNECTOR
1. Check the BEKIORN (158) wires for an
open (see schematic).
)-I: BOOR AJAR SHORTED SWITCH
TEST
Disconnect the suspect Door Ajar Switch
a1 A Connector. Switch the Ignition to
RUN and observe the Door Ajar
Indieator
segment of the vehicle symbol on the DIC.
@ If the Door Ajar segment is now off and the
suspect DOOR AJAR message is not
displayed, replace the Door Ajar Switch.
If the Door Ajar segment lights and the
suspect DOOR
AJAR message is
displayed, check the wire at
terminal A for a
short to ground (see schematic).
(Continued on next page)

DRIVER INFORMATION CENTER (DIC) I $
(Continued from previous page)
I: DOOR AJAR OPEN SWITCH TEST
At: SUSPECT DOOR AJAR SWITCH
CONNECTOR (Disconnected)
(see schematic).
2. Check the wire at terminal B for an open
(see schematic).
CIRCUIT OPERATION
The Driver Information Center (DIC) dis-
plays warnings about
saftey conditions in the
vehicle. The location of the condition is indi-
cated in a car symbol, where segments of the
symbol are
lit. Seven displays that form letters
light up to spell out the condition, such as LOW
COOLANT. The car symbol and the letters are
made by Liquid
Crystal Displays (LCD) that
are turned on by a solid state microprocessor.
Door and trunk switches that are closed with
the door open (like interior light switches) are
connected to the DIC Display. These ground
the DIC inputs if the door or trunk is not closed
tightly, and then the display illuminates the
warning. The Washer Fluid Level Switch works
in the same way.
It closes when the windshield
washer fluid is low.
The Low Coolant Probe is not a switch that
opens and closes.
It has a very high resistance
to ground, more than 50,000 ohms, when the
engine coolant level is low. This causes the DIC
Display to light the LOW COOLANT w
With more of the probe covered by coolant, its
resistance decreases. When the fluid level is
good, the resistance
will be less than 10,000
ohms. With the probe resistance between
10,000 and 50,000 ohms, the probe is partly
covered and the fluid is not low enough to cause
the warning to be displayed. Burned
out light bulbs in the vehicle are
detected by the Lights Monitor. The power feed
from a switch to a bulb circuit contains
resistance wire. This is connected between the
switch and the Lights Monitor Module.
If the
bulb is on properly, the current through the
resistance wire causes a small voltage drop, less
than one volt. When a bulb burns out, there is
no current through it
and the voltage drop at
the module is missing. The Lights Monitor
Module detects this battery voltage at one of its
inputs (instead of slightly lower voltage) and
closes a solid state switch in the Module to
g to appear in the DIC Display.