Initial Inspection and Diagnostic Overview
Checking the BasicsAll troubleshooting must begin by "CHECKING THE BASICS". Certain basic faults can be undetectable by the self-diagnostic system of the ACC/TCC control unit, if applicable.
COMPLAINT VERIFICATION
Whenever possible the repairing technician should personally verify the complaint.
MALFUNCTION VERIFICATION
Today's sophisticated automotive systems are easily misunderstood, which can lead to repairs that attempt to force a particular system to perform in a way that it was never intended to operate. Therefore, the troubleshooting technician should compare the actual system operation to the nominal system operation. Furthermore, the technician is also encouraged to compare the problem vehicle system operation with a known good vehicle.
PRIOR TO ANY TEARDOWN, REPAIR, OR COMPONENT REPLACEMENT, the following steps should always be considered:
PREVIOUS REPAIRS
The vehicle repair history can provide explanations to unusual complaints, which seem to elude normal troubleshooting attempts. Incorrect components or unapproved repairs can have subtle influences on seemingly unrelated systems.
POWER SUPPLY RELAYS
Relays as well as their plug connections can be a source of intermittent operation.
TEMPERATURE SENSORS AND SWITCHES
Temperature sensors and switches should be checked for physical condition and proper installation as well as electrical reliability.
MAINTENANCE
Drive belts, coolant, and the receiver drier should be replaced at scheduled maintenance periods. Coolant and refrigerant levels must be correct. Maintenance to prevent restricted air flow at the radiator and condenser, and the interior air inlet and outlets should be should be performed.
BATTERY STATE OF CHARGE
Batteries in a state of partial discharge can have a dramatic effect on ACC 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 ELECTRICAL AND 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.
POWER TRAIN CABLE ATTACHMENTS
Metal cables attached to the engine or transmission, which appear overheated and/or discolored indicate the need to thoroughly test all ground connections.
ENGINE PERFORMANCE
An engine in poor running order may cause the vacuum system of the A/C, ACC or TCC system to operate sporadically.