Section 90 (Engine Control System - Tests W/Codes - Introduction): Introduction

WARNING: This page does not describe the selected car, but rather 68 other vehicles, including the 1999 Saturn SW2, 1999 Saturn SW1, 1999 Saturn SL2, 1999 Saturn SL1, and 1999 Saturn SL. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: The Service Engine Soon (SES) lamp is also refered to as Malfunction Indicator Lamp (MIL).

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 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, go to DIAGNOSTIC PROCEDURE under SELF-DIAGNOSTIC SYSTEM. If no fault codes are present and driveability problems exist, go to appropriate TROUBLE SHOOTING - NO CODES article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.). If only intermittent codes are present, see INTERMITTENTS in appropriate TROUBLE SHOOTING - NO CODES article.