Engine Controls - Trouble Shooting - No Codes: Introduction

NOTE: Most all ignition and fuel system problems that can affect engine performance are monitored by Trionic T-5 and T-7 Engine Management Systems, and will set a diagnostic code if a malfunction occurs. This article is a general guide to help diagnose system problems on any vehicle, and is not specific to Saabs.

Before diagnosing symptoms or intermittent faults, perform steps in BASIC DIAGNOSTIC PROCEDURES and SELF-DIAGNOSTICS articles. Use this article to diagnose driveability problems existing when a hard fault code is not present.

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.

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.

NOTE: For specific testing procedures, see SYSTEM & COMPONENT TESTING article.