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.

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

Tests W/O Codes: Introduction

Use the Manual With the Right Hardware

When to See a Mechanic

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