Engine Controls - Self-Diagnostics: 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 checks and inspections covered in appropriate BASIC 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 DTCs are present and driveability problems exist, proceed to appropriate TROUBLE SHOOTING - NO CODES article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.). If only intermittent DTCs are present, see INTERMITTENTS in appropriate TROUBLE SHOOTING - NO CODES article.