Diagnostic Strategies

COMPLAINT VERIFICATION
Whenever possible the technician should personally verify the complaint. Having experienced the malfunction, you will be less likely to attempt to repair a non-existent fault.

MALFUNCTION VERIFICATION
Automotive control systems are easily misunderstood, leading to repairs that attempt to force a system to perform in a way that was never intended.
^ Always compare system operation to normal system operation as described in the owner manual or Description and Operation.
^ When possible, compare vehicle operation with a known good vehicle.

PREVIOUS REPAIRS
Vehicle repair history can provide explanations to unusual complaints which elude normal troubleshooting attempts. Incorrect components or unapproved repairs can have subtle influences on seemingly unrelated systems.
^ Always attempt to get the "whole story" from the customer.
^ When possible, check the system or component that was last repaired.