Fuel Injector Circuit Diagnosis

Fuel Injector Circuit Diagnosis

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.



Diagnostic Fault Information






Circuit/System Description

The control module enables the appropriate fuel injector pulse for each cylinder. Ignition voltage is supplied to the fuel injectors. The control module controls each fuel injector by grounding the control circuit via a solid state device called a driver.


Reference Information
Schematic Reference

Engine Controls Schematics (Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information
Special Tools

J 44603 Injector Test Lamp


Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at a fuel injector.
2. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal 1 or A and ground.

• If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ignition circuit fuse is open, test or replace the fuel injector.

3. Ignition OFF, connect a J 44603 between the control circuit terminal 2 or B and the ignition circuit terminal 1 or A of each fuel injector, one at a time.
4. Engine cranking, the test lamp should flash for each injector.

• If the test lamp is always ON, test the appropriate control circuit for a short to ground. If the circuit tests normal, replace the ECM.


• If the test lamp is always OFF, test the appropriate control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.

5. If all circuits test normal, test or replace the fuel injector. Refer to Fuel Injector Diagnosis (w/J39021 or w/Tech 2) (Fuel Injector Diagnosis (w/J39021 or w/Tech 2))Fuel Injector Diagnosis (w/CH47976) (Fuel Injector Diagnosis (With CH 47976)) .



Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Fuel Injector Replacement (Service and Repair)
* Control Module References (Programming and Relearning) for ECM replacement, setup, and programming