Engine Control System & Engine Component Tests - 4.0L Engine: Introduction

Before testing separate components or systems, perform procedures in BASIC TESTING - 4.0L 6-CYL article. Since many computer-controlled and monitored components set a trouble code if they malfunction, also perform procedures in appropriate TESTS W/CODES - 4.0L 6-CYL article.

NOTE: Testing individual components does not isolate possible short or open circuits. Unless stated otherwise in test procedure, perform all voltage tests with a Digital Volt-Ohmmeter (DVOM) having a minimum 10-megohm input impedance. Use ohmmeter to isolate wiring harness short or open circuits.