Engine Controls - System & Component Tests: Introduction

Before testing separate components or systems, perform all procedures listed in BASIC DIAGNOSTIC PROCEDURES - TRUCKS - EXCEPT TRACKER article. Since many computer-controlled and monitored components will set a Diagnostic Trouble Code (DTC) if they malfunction, it is also recommended self-diagnostics be performed. See appropriate SELF-DIAGNOSTICS article.

NOTE: Testing individual components does not isolate shorts or opens. Perform all voltage tests with a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance, unless stated otherwise in test procedure. Use ohmmeter to isolate wiring harness shorts or opens.