DESCRIPTION
SERVICE MANUAL NUMBER 22
Page 5A-6
90-860074--1 FEBRUARY 2002
General Information
Basic Knowledge and Tools Required
To use the information in this manual most effectively, a general understanding of basic
electrical circuits and circuit testing tools is required. You should be familiar with wiring
diagrams; the meaning of volts, ohms and amperes; the basic theories of electricity and
understand what happens in an open or shorted wire. To perform system diagnosis, several
special tools and equipment are required. Please become acquainted with the tools and
their use before attempting to diagnose the system. Special tools, which are required for
system service, are listed in the particular sections.
Visual/Physical Inspection
IMPORTANT: A careful visual and physical inspection must be performed as part of
any diagnostic procedure. This can often lead to fixing a problem without further
steps.
Inspect all lines and hoses for correct routing, pinches, cuts or disconnects. Inspect
components that are difficult to see. Inspect all the wires in the engine compartment for
proper connections, burned or chafed spots, pinched wires or contact with sharp edges or
hot exhaust manifolds. This visual/physical inspection is very important. It must be done
carefully and thoroughly.
Electrostatic Discharge Damage
Electronic components used in control systems are often designed to carry very low voltage,
and are very susceptible to damage caused by electrostatic discharge. It is possible for less
than 100 volts of static electricity to cause damage to some electronic components. By
comparison, it takes as much as 4,000 volts for a person to even feel the effect of a static
discharge.
There are several ways for a person to become statically charged. The most common
methods of charging are by friction and by induction. An example of charging by friction is
a person sliding across a seat, in which a charge of as much as 25,000 volts can build up.
Charging by induction occurs when a person with well-insulated shoes stands near a highly
charged object and momentarily touches ground. Charges of the same polarity are drained
off, leaving the person highly charged with the opposite polarity. Static charges of either type
can cause damage; therefore, it is important to use care when handling and testing
electronic components.
