Engine Controls - Tests W/Codes - 7.3L Diesel: Introduction

WARNING: Ensure negative battery cables are disconnected before disconnecting engine wiring harness. The Injector Driver Module (IDM) supplies 115-volts DC into each fuel injector connected to engine wiring harness. Severe electrical shock hazard exists. DO NOT pierce wires.

If no diagnostic trouble codes or only pass codes (system functioning properly) are found during self-diagnostics, proceed to TESTS W/O CODES - 7.3L DIESEL article for diagnosis by symptom.