Pontiac Fiero 1988 Service Manual page 935

TROUBLESHOOTING PROCEDURES
The following four-step troubleshooting pro-
cedure is recommended:
Step 1 : Check the problem.
Perform a System Check to be sure you
understand what's wrong. Don't waste'time
fixing part of the problem! Do not begin dis-
assembly or testing until you have narrowed
down the possible causes.
Step 2: Read the Electrical Schematic.
Study the schematic. Read the Circuit Oper-
ation text if you do not understand how the
circuit
should
work. Check circuits that share
wiring with the problem circuit. The names of
circuits that share the same fuse, ground,
switch, etc., are included on each electrical
schematic. (Shared circuits are also shown on
Power Distribution, Ground Distribution,
Fuse Block Details, and Light Switch pages.)
Try to operate the shared circuits. If the
shared circuits work, then the shared wiring is
OK. The cause must be within the wiring used
only by the problem circuit. If several circuits
fail at the same time, chances are the power
(fuse) or ground circuit is faulty.
Step
3 :
Find
the Cause and Repair.
® Narrow down the possible causes.
• Use the Troubleshooting Hints.
• Make the necessary measurements as
given in the System Diagnosis.
• Before you replace a component, check
power, signal, and ground wires at the
component harness connector. If these
are OK, the component must be bad.
Step 4: Test the Repair
Repeat the System Check to be sure you
have fixed the whole problem.
Example
A customer brings in a car and says that the
high beams do not work.
Step
1:
Perform a System Check on the Head-
lights Circuit. You may discover that both low
beams operate. In "Hi/' you may notice that
the High Beam Indicator comes on, but neither
high beam operates.
1 T A N
n
1 LTGRN
LH
IADLIGHT
LI G HTS:
2 B 1 K
^
T U R N / 5 B L K
1 5 0 HAZARD/ W
1 5 1
P A R K
2BLK I 1 5 0
G 1 0 9
Figure 9 - Typical Headlights Schematic