Tests W/O Codes: Introduction

Before attempting to diagnose any symptoms or intermittent faults, make sure test procedures in the appropriate BASIC TESTING and TESTS W/CODES (if applicable) articles have been performed. Use this article to diagnose driveability problems that exist when a hard fault code is not present or vehicle is not equipped with a self-diagnostic system.

Symptom checks are intended to direct the technician to malfunctioning component(s) so that further diagnosis may be performed. A "symptom" should lead to further testing of specific components or systems, or verification of adjustment specifications.

Use intermittent test procedures to locate intermittent driveability problems that do not occur when the vehicle is being tested. These problems may cause a noticeable driveability problem or cause the "malfunction" warning light to illuminate on some vehicles.

It is also possible that certain driveability concerns have been rectified by the manufacturer through substitution of a revised calibration chip or computer control unit. Check with manufacturer for latest information on updated chips and control units.

NOTE: For specific component or system test procedures, see the SYSTEM/COMPONENT TESTS article. For specifications, refer to the SPECIFICATIONS article. For tune-up procedures, refer to the ADJUSTMENTS article.