Engine Control System - Tests W/O Codes: Introduction

NOTE: Models may use a Powertrain Control Module (PCM) or Vehicle Control Module (VCM). The term PCM will be used in this article to describe all control modules.

Before diagnosing symptoms or intermittent faults, perform basic diagnostic procedures in the BASIC TESTING article and self-diagnostic steps in the TESTS W/CODES article. Use this article to diagnose driveability problems if a current trouble code is not present or if not equipped with a self-diagnostic system.

Symptom checks are intended to direct technician to malfunctioning component(s) for further diagnosis. A symptom should lead to a specific component or system test, or an adjustment specification. Use intermittent test procedures to locate driveability problems not occurring when vehicle is being tested.

NOTE: For specific testing, see SYSTEM/COMPONENT TESTS article. For specifications, see the ADJUSTMENTS article or SPECIFICATIONS article.

NOTE: SERVICE ENGINE SOON light, located on instrument cluster, is also referred to as the Malfunction Indicator Light (MIL).