1988 PONTIAC FIERO Service Repair Manual

INTRODUCTION 1:
This manual contains the following kinds of
diagnostic information:
e Electrical Schematics
Component Location Lists
@ Harness Connector Faces
@ ?koubleshooting Hints
@ System Checks
System Diagnoses
@ Circuit Operation Descriptions
@ Harness Routing Views
Using these elements together will make elec-
trical troubleshooting faster and easier. Each
element is described below.
The Electrical
Seher~latic should always be
your starting point in using this Electrical
Troubleshooting Manual. The schematic shows
the electrical current paths when a circuit is
operating properly. It is essential to under-
stand how a circuit
should work before trying to
figure out why it doesn't.
The Harness Connector Faces show the cav-
ity or terminal locations in all the multi-pin
connectors shown in the schematic. Together
with the wire colors and terminals given in the
schematic, they help you locate test points. The
drawings show the connector faces you see
after the harness connector has been discon-
nected from a component. When more than one
connector is connected to a component the con-
nectors are all shown together.
The Troubleshooting Hints offer short-cuts
or checks to help you determine the cause of
a
complaint. They are not intended to be a rigid procedure
for solving an electrical situation.
Rather, Troubleshooting Nints represent a
common-sense approach, based on an under-
standing of the circuit.
The System Check gives a summary of how
the circuit should be operated and what should
happen. This is especially important when you
are working on a new system. The System
Check will help you identify symptoms, lead
you to diagnosis and confirm the system after
repair.
The System Diagnosis provides a procedure
to follow that will locate the condition in a cir-
cuit. If your own knowledge of the system and
the Troubleshooting Hints have not produced
a
quick fix, follow the System Diagnosis. All pro-
cedures are based on symptoms to assist you in
locating the condition as fast as possible.
The Circuit Operation will help you under-
stand the circuit. It describes the components
and how the circuit works.
The Component Location List helps you find
where the parts of the circuit are in the vehicle.
A brief statement of the location is given and
also a reference to a drawing that shows the
component and its connecting wires. These
Colnponent Location Views are in cell 201.
Harness Routing Views are found in cell 203.
These views show the routing of the major wir-
ing harnesses and the in-line connectors
between the major harnesses. These views will
make troubleshooting easier when you are not
sure about harness routing.
PAGE NUMBER
This section is organized into cells with most
cells containing a circuit schematic and the text
for that circuit. This makes the section easy to
use, since the page number for a schematic will
normally stay the same year after year, and it
will also be the same in
all the GM publications
about that circuit. For example, the Cruise Con-
trol schematics will always be the first pages of
cell 34. The other information for Cruise Con-
trol follows them on pages
34-2,34-3, etc.
Some cells may have more than one circuit
schematic, such as Power Distribution, Interior
Lights, and Air Conditioning. The circuit you
want can either be located by using the index, or
by a quick look through the related cell.
All the engine circuits for a particular engine
VIN type are in the same cell. This makes that
cell easy to use, since schematics for other cars
are not in your way. The instrument panel sche-
matics are organized similarly. If you are work-
ing on a car with a Digital Cluster, only the
schematics that apply to that car's Digital
Cluster will be in the cell you use. Information
on the Indicators and Gages Clusters will be in
other cells.

These schematics break the entire electrical
system down into individual circuits. You are
not distracted by wiring which is not part of
the circuit you're working on.
It is important to realize that no attempt is
made on the schematic to represent compo-
nents and wiring as they physically appear on
the car. For example, a 4-foot length of wire is
treated no differently in a schematic from one
which is only a few inches long. The number of
cavities for each connector is listed in the Com-
ponent Location List. Similarly, switches and
other components are shown as simply as pos-
sible, with regard to function only.
The following example shows how to read a
Worn schematic, see figure
1. Locate the Horn
schematic using the Index. The circuit sche-
matic will look somewhat like the one to the
right. The schematic is read from top to bot-
tom.
Voltage is applied to the Horn Relay at all
times. When the relay coil is grounded by clos-
ing the Horn Switch, the relay contacts close.
When the relay contacts are closed, both the
LH and
RH Horns are energized.
1 HORN
SEE FUSE
I BLOCK DETAILS
Figure 1 - Typical Horn Schematic

INTRODUCTION
COMPONENT LOCATIONS
When you are ready to locate the schematic
components on the car, use the Component
Locations List, see figure 2.
Listed in the left hand column are the com-
ponents shown on the schematic. Next to the
Convenience Center is the location, "Under
LH side of
I/P." Reference to LH and RH is
made as though the troubleshooter
was sitting
in the driver's seat. On the same line, in the far
right column, is a page-figure reference. In this
case, you are directed to figure
A on page 201-6.
Where connectors are listed, the number of
cavities is provided. This represents the total
number of cavities in the connector, regardless
of how many are actually used. This informa-
tion is provided to help you identify connec-
tors on the car.
Grounds are listed next in the table. The
location description for
GlOl reads, "LH front
of engine compartment, behind headlights
panel. "You are directed to page 201-8, figure D.
Nearly every component, connector, ground
or splice shown on a schematic can be pin-
pointed visually by using the Component Loca-
tion Views' figures.
COMPONENT LOCATION Page-Figure
COMPONENTS
........................ Convenience Center .............. Under LH side of IIP 201-6-A
..................... ........................ Fuse Block Under LH side of IIP 201-6-A
....................... Horn BrushISlip Ring ............ Under steering wheel. 201-5-E
....................... Horn
Switch .................... Under steering wheel. 201-5-E
CONNECTORS
............................ ................ ClOO (46 cavities)
LH side of dash 201-5-B
................ .............. C201 (11 cavities) Under
LH side of IIP, near C100. 201-5-F
GROUNDS
.......................... GlOl LH front of engine compartment, behind
.......................... headlights panel. 201-8-D
SPLICES
.......................... S139. Front lights harness, behind LH front light panel 201-8-C
.......................... S212. IIP harness, behind IIP, above steering column. .. 201-6-B
Figure 2 - Typical Entries In The Component Location List

INTRODUCTION
HARNESS CONNECTOR FACES
The connectors, see figure 3, are labeled with
the component they are connected to, or the
connector number from the schematic where
they appear, and their color. The identifying
number is for reference only; it is not the con-
nector part number. For in-line connectors, the
half shown is usually the Socket half. If both
views are shown, the other half is the Pin
Half.
Only connectors that have two or more termi-
nals are shown.
If you need to backprobe a connector while it
is on the component, the order of the terminals
must be mentally reversed. The wire color is a
help
in this situation. If there is more than one
wire of the same color, you may need to locate a
test point from its terminal number.
A useful
trick is to imagine that you are probing a termi-
nal from behind the page you are looking at.
Then mentally locate that terminal with respect
to the keyway or other reference mark.
v03000.2 Blower Motor
C3 BLU
C2 WHT
C1 BLK
v00010.0
Radio
BLU 12015196
Horn Relav
Figure 3 -Typical Harness Connector Faces

INTRODUCTION
OTHER INFORNlATlORl
Body Part Names
Refer to figure 4 for the correct body part
names.
VIN References
If schematics for more than one variation of
an engine type-V6, for example--are shown,
then the schematics will be labeled with VIN
designations to distinguish the variations.
Service Parts Identification Label
To aid service and parts personnel in identi-
fying options and parts originally installed. a
Service Parts Identification Label has been
REAR
PANEL
placed in the car. See the General Information
Section OA of the Chassis Service Manual for
Figure 4 - Body Part Names
the location of the label and the definition of
the option codes.
Abbreviations
AIC - Air Conditioning
BCbl - Body Computer Module
ECM
- Electronic Control Module or Engine
Control Module
IIP
- Instrument Panel
RH
- Right Hand. as seen from driver's seat
LH
- Left Hand
Not Used
- The connector cavity has no func-
tion.

INTRODUCTION
Power Distribution
The Power Distribution schematic shows
the wiring from the Battery and Generator to
the Starter Solenoid, Fuse Block, Ignition
Switch and Light Switch. The first component
after a Fusible Link is also shown. In certain
instances, the first component after a Fuse
Block fuse and Light Switch is also shown.
The Power Distribution schematic refers to
Fuse Block Details and Light Switch Details
schematics. By using these three
(3) schemat-
ics, power distribution wiring can be followed
from the Battery and Generator to the first
component after a Fusible Link. Fuse and
Light Switch. The ability to follow the power
distribution wiring to the first component in
each circuit is extremely helpful in locating
short circuits which cause fusible links and
fuses to open.
Figure
5 is a sample Power Distribution sche-
matic.
It shows how voltage is applied from the
positive Battery terminal to the various cir-
cuits on the car. For example, Battery voltage
is applied to the Starter Solenoid, Fusible Link
D, the
RED wire and connector ClOO to Fuse 1
and Fuse 2 in the Fuse Block and the Light
Switch in the
LH Pod. These fuses are said to be
"Not At All Times", since Battery voltage is
always applied to them.
Notice that Battery voltage is
also applied
to Fusible Link
F and the RED wire to the
Coolant Fan Relay.
L4VIN U 1 ELK I
i VSVIN L 32 BLK
DISTRIBUTION
SkE LIGHT
HEADLIGHT
--
PAGE 100 0 BLOCK DETAILS PAGE 11 2
Figure 5 -Typical Power Distribution Schematic

INTRODUCTION
Fuse Block Details
The Fuse Block Details schematic, see fig-
ure
6, shows all the wiring between a fuse and
the components connected to the output of the
fuse. In certain instances where space permits,
this detail is shown on the Power Distribution
schematic. The Fuse Block Details schematic
is extremely helpful in locating
a short circuit
that causes a fuse to open.
COURTESY LIGHTS CONSOLEREAR DOOR COURESTY PAGE110 0 COURTESY LIGHT
RELAY - PAGEllO 0 PAGE151 0
Figure 6 - Typical Fuse Block Details Schematic

INTRODUCTION
Light Switch Details output of the Light Switch. In certain matic helps you understand the many wires
The Light Switch Details schematic, see
fig- instances where space permits, some of this
that come from the Light Switch. This sche-
ure 7, shows the wiring between the Light detail
may be shown on the Power Distribution matic is also helpful in locating a short circuit
Switch and the components connected to the schematic.
The Light Switch Details
sche- that causes the fuse ahead of the Light Switch
to open.
LIGHT SWITCH DETAILS ,' '6--- ----- --- 5""l LIGHT