Fuel Injector Circuit Diagnosis

Fuel Injector Circuit Diagnosis

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions 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 [1][2]Electrical Diagrams
Connector End View Reference

Component Connector End Views Connector End Views By Name
Electrical Information Reference

* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs

Scan Tool Reference

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

J 44603 - Injector Test Lamp

Circuit/System Verification

Engine idling, observe the following control circuit status parameters for each fuel injector:

* Injector Ckt Short Gnd Test Status
* Injector Ckt Open Test Status
* Injector Ckt Short Volts Test Status

• Each parameter should toggle between OK and Not Run or Not Run and OK.

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 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 - Injector Test Lamp between the control circuit terminal B and the ignition circuit terminal 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 engine control module (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 Solenoid Coil Test Fuel Injector Solenoid Coil Test.

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 replacement, setup, and programming