Engine Controls - Trouble Shooting - No Codes: Introduction

Before diagnosing symptoms or intermittent faults, perform preliminary inspection and steps in appropriate SELF-DIAGNOSTICS article. Use this article to diagnose driveability problems existing when a hard trouble code is not present.

NOTE: Some driveability problems may have been corrected by manufacturer with a revised Engine Control Module (ECM). Check with manufacturer for latest ECM application.

Symptom checks can direct the technician to malfunctioning component(s) for further diagnosis. A symptom should lead to a specific component, system test or adjustment. See SYMPTOMS .

Use intermittent test procedures to locate driveability problems that do not occur when the vehicle is being tested. These test procedures should also be used if a soft (intermittent) trouble code was present but no problem was found during self-diagnostic testing. See INTERMITTENTS .

NOTE: For specific testing procedures, see SYSTEM & COMPONENT TESTING article. For specifications, see ON-VEHICLE ADJUSTMENTS or SERVICE & ADJUSTMENT SPECIFICATIONS article.

Many computer-controlled and/or monitored components set a Diagnostic Trouble Code (DTC) if they malfunction. In this event testing is incorporated in self-diagnostics testing. For testing procedures, see appropriate SELF-DIAGNOSTICS article. For systems and components not covered in this article, use self-diagnostics testing procedures.

For aid in locating components, see component location illustrations in REMOVAL, OVERHAUL & INSTALLATION article.