Engine Controls - Trouble Shooting - No 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 - LEXUS article in GENERAL INFORMATION before disconnecting battery.

NOTE: Some driveability problems may have been corrected by manufacturer with a revised computer control unit. Check with manufacturer for latest computer application.

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

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 Diagnostic Trouble Code (DTC) is not present.

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.

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.