Engine Controls - Trouble Shooting - No Codes: Introduction

CAUTION: This article should only be used when directed to by the POWERTRAIN CHART 1: POWERTRAIN SYSTEM CHECK in SELF-DIAGNOSTICS - ALLANTE article. The POWERTRAIN CHART 1: POWERTRAIN SYSTEM CHECK must always be performed first. Failure to follow these guidelines may result in incorrect or unnecessary diagnosis.

Performing the POWERTRAIN CHART 1: POWERTRAIN SYSTEM CHECK in SELF-DIAGNOSTICS - ALLANTE article first, may lead to a DTC flow chart or some other easily diagnosed problem. If no other clues to the root cause of a customer complaint are apparent, the POWERTRAIN SYSTEM CHECK will refer to the charts in this article which indicate what subsystems and components should be checked. These charts are not meant to be component replacement lists. Each subsystem or component should be checked for proper operation and repaired or replaced only if they are not operating properly.

If directed to this article from the POWERTRAIN SYSTEM CHECK or diagnosis in another article, select the symptom with the description that best fits the customer complaint. See SYMPTOMS . Then begin performing the tests suggested and proceed until the root cause is found. The suggested tests are generally listed in order of probability and/or ease of diagnosis. The tests need not be performed in the listed order, though. If you have already performed one of the tests listed, there is no need to perform it a second time.

When referred to diagnosis in another article, perform the test listed and if the test does not lead to a problem, return to this article and continue where you left off.

NOTE: Before diagnosing symptoms or intermittent faults, ensure that SELF-DIAGNOSTICS SYSTEM CHECK in SELF-DIAGNOSTICS - ALLANTE article has been performed. If no Diagnostic Trouble Codes (DTCs) are present and a no start condition exists, proceed to BASIC DIAGNOSTIC PROCEDURES -- ALLANTE article. If no DTCs are present and a driveability condition exists, diagnosis by symptom (i.e., ROUGH IDLE, ENGINE STALLS, etc.).

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

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.

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