Engine Controls - Tests W/O Codes: Introduction

CAUTION: When battery is disconnected, vehicle computer and memory systems may lose memory data. Driveability problems may exist until computer systems have completed a relearn cycle. See COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION before disconnecting battery.

Before diagnosing symptoms or intermittent faults, perform steps in BASIC DIAGNOSTIC PROCEDURES article and appropriate SELF-DIAGNOSTICS article. Use this article to diagnose driveability problems existing when a hard Diagnostic Trouble Code (DTC) is not present.

Before diagnosing symptoms or intermittent faults, follow proper workflow. See ON-BOARD DIAGNOSTICS under SELF-DIAGNOSTIC SYSTEM in appropriate SELF-DIAGNOSTICS article. If no Diagnostic Trouble Codes (DTC) are present and a no-start condition exists, proceed to BASIC DIAGNOSTIC PROCEDURES article. If no DTCs are present and a driveability condition exists, diagnose by symptom (i.e., ROUGH IDLE, ENGINE STALLS, etc.). Symptom checks direct technician to malfunctioning component(s) for further diagnosis. A symptom should lead to a specific component, system test or an adjustment.

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 DTC code is present, but no problem is found during self-diagnostic testing.

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