Chapter 25 Computer System Service 417
Use a voltmeter to make sure the correct refer-
ence voltage is being sent to a sensor. Most comput-
ers produce a reference voltage of about 5 volts. If
the reference voltage is not correct, check the wiring
before condemning the computer. You can also mea-
sure voltage to make sure the correct voltage output
is being fed to the actuators.
Each computer input and output passes
through an individual metal terminal, or pin,
which plugs into the vehicle wiring harness. Pin
numbers identify the location and purpose (elec-
trical value and internal connection) of each ter-
minal in a computer wiring harness connector.
You may have to probe computer terminal pins to
A
C
B
D
Relay
Locking
pin
Figure 25-10. Relays have moving parts that can fail in service. Relays can be located almost anywhere on the vehicle. A—
Technician has removed the rear seat cushion to gain access to the fuses and relays. B—This relay has a locking pin that must be
removed before disconnecting the harness. C—Relays can have different internal construction. Make sure the replacement unit is
identical to the original. D—The service manual will give relay locations for pinpoint testing and replacement.