Engine Control Systems 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 checks and inspections covered in the BASIC TESTING - 3.8L article. Failure to do so may result in lost diagnostic time.

If no faults found performing procedures in the BASIC TESTING - 3.8L article, proceed with DIAGNOSTIC PROCEDURE  under SELF-DIAGNOSTIC SYSTEM. If no fault codes are present and driveability problems exist, proceed to the 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 the TESTS W/O CODES article.