Section 1 (Engine Controls Tests W/Codes - Diesel): Introduction

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The Powertrain Control Module (PCM) controls EGR system operation, Torque Converter Clutch (TCC) engagement, transmission, fuel control and fuel injection timing. The PCM also monitors a number of transmission functions and uses the data to control shift solenoids, TCC, and pressure control solenoid to regulate upshift pattern, downshift pattern and line pressure (shift quality).

Most engine/transmission control problems are not computer related, but result from mechanical breakdowns, poor electrical connections, or damaged vacuum hoses. Before condemning the computer system, carefully perform visual and mechanical inspections covered in appropriate BASIC DIAGNOSTIC PROCEDURES article. Failure to perform these inspections can result in lost diagnostic time.

If no faults were found while performing visual and mechanical inspections in appropriate BASIC DIAGNOSTIC PROCEDURES article, proceed with DIAGNOSTIC PROCEDURE under SELF-DIAGNOSTIC SYSTEM. If no Diagnostic Trouble Codes (DTCs) are present and driveability problems exist, proceed to appropriate TROUBLE SHOOTING - NO CODES article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.). If only intermittent codes are present, see INTERMITTENTS in appropriate TROUBLE SHOOTING - NO CODES article.