Section 128 (Engine Controls - Basic Diagnostic Procedures - 6.5L Diesel): Summary
WARNING: This page is about a different car, the 1998 GMC Pickup, 1998 GMC Cab & Chassis, 1998 Chevrolet Pickup, and 1998 Chevrolet Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.
If no faults were found while performing BASIC DIAGNOSTIC PROCEDURES, no trouble codes (or only intermittent ones) were found while performing ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK and driveability problems exist, proceed to TESTS W/O CODES - 6.5L DIESEL article for diagnosis by symptom (i.e., ROUGH IDLE, NO-START, etc.) or intermittent diagnostic procedures.