Engine Controls - Basic Diagnostic Procedures: Introduction
The following diagnostic steps help prevent overlooking a simple problem. This is also where to begin diagnosis for a no-start condition.
The first step in diagnosing any driveability problem is verifying the customer's complaint with a test drive under the conditions the problem reportedly occurred.
Before entering self-diagnostics, perform a careful and complete visual inspection. Most engine control problems result from mechanical breakdowns, poor electrical connections or damaged/misrouted vacuum hoses. Before condemning the computerized system, perform each test listed in this article.
CAUTION:
Ensure ignition switch is in OFF position when disconnecting ECM or performing resistance tests.
NOTE:
Perform all resistance and voltage tests using a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm impedance, unless stated otherwise in test procedures.
NOTE:
For wire color identification, see appropriate wiring diagram in
WIRING DIAGRAMS article.