Engine Control System Tests W/O Codes: Introduction

Before diagnosing symptoms or intermittent faults, perform steps in the BASIC TESTING and perform testing procedures in the TESTS W/CODES articles. Use this article to diagnose driveability problems existing when a hard fault code is not present.

Symptom checks can direct the technician to malfunctioning component(s) for further diagnosis. A symptom should lead to a specific component, system test or adjustment.

Use intermittent test procedures to locate driveability problems that DO NOT occur when the vehicle is being tested. These test procedures should also be used if a soft (intermittent) trouble code was present, but no problem was found during self-diagnostic testing.