Checking the Basics

Prior to any teardown, repair or component replacement, the following steps should always be considered.

COMPLAINT VERIFICATION
Whenever possible the repairing technician should personally verify the complaint. Having experienced the malfunction, the technician is less likely to try to repair non-existent faults.

MALFUNCTION VERIFICATION
Today's sophisticated automotive systems are easily misunderstood. The troubleshooting technician should compare the system operation to the nominal system operation as described in the section Description and Operation. Furthermore, the technician is also encouraged to compare the problem vehicle system operation with a known good vehicle. Description of On-Board Diagnostics

PREVIOUS REPAIRS/MODIFICATIONS
The vehicle repair history can provide explanations to unusual complaints which seem to elude normal troubleshooting attempts. Incorrect components, unapproved repairs or modifications can have subtle influences on seemingly unrelated systems.

NOTE: Vehicles with a history of accident damage and repair may exhibit very unusual symptoms.

BATTERY STATE OF CHARGE
Batteries in a state of partial discharge can have a dramatic effect on control units and related components.

POSITIVE BATTERY CABLE INTEGRITY
All B+ connections must be in perfect condition for trouble-free electronic system operation. Refer to Electronic Diagrams for B+ interconnects.

FUSIBLE LINK INTEGRITY
Fusible links are employed to prevent possible damage to electrical components and wiring harnesses. These links and their connections must be without dynamic resistance. Dynamic resistance can only be checked using the voltage drop method of testing.

NEGATIVE GROUND CONNECTIONS
As all electrical circuits are a circle, all B- connections must also be checked and verified to be in perfect condition. A poor "common" ground point will cause seemingly unrelated systems to influence one another. High current systems which encounter a poor "common" ground can back feed through other electrical systems causing unusual operation and perhaps inexplicable component failure. As with the B+ side of the electrical system, the ground side should be checked dynamically using the voltage drop technique.