Engine Controls - System & Component Testing 4.6L & 5.4L: Introduction

Before testing separate components or systems, perform BASIC DIAGNOSTIC PROCEDURES in appropriate article:

For Expedition 4.6L, see BASIC TESTING - 4.6L .
For Expedition 5.4L, see BASIC TESTING - 5.4L .
For Navigator, see BASIC TESTING .

Since many computer-controlled and monitored components set a Diagnostic Trouble Code (DTC) if they malfunction, also perform SELF-DIAGNOSTICS in appropriate article:

For 4.6L vehicles, see TESTS W/CODES - 4.6L article.
For 5.4L vehicles, see TESTS W/CODES - 5.4L article.

NOTE: Testing individual components does not isolate short or open circuits. 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 shorted or open wiring harness.

NOTE: For identification of circuits and terminals referenced in test procedures, see appropriate WIRING DIAGRAMS article.