Engine Control System - Tests W/Codes: Introduction

Most engine control problems are the result of mechanical breakdowns, poor electrical connections or damaged vacuum hoses. Before considering the computer system as a possible cause of problems, perform basic diagnostic procedures in the BASIC ENGINE DIAGNOSTIC PROCEDURES article. Failure to do so may result in lost diagnostic time.

If no faults were found while performing basic diagnostic procedures, proceed with DIAGNOSTIC PROCEDURE  under SELF-DIAGNOSTIC SYSTEM. If no fault codes are present and driveability problems exist, proceed to ENGINE CONTROLS - TESTS W/O CODES article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.). If only intermittent codes are present, see INTERMITTENTS in ENGINE CONTROLS - TESTS W/O CODES article.