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 engine control module (ECM) enables the appropriate fuel injector pulse for each cylinder. Ignition voltage is supplied to the fuel injectors. The ECM 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 Fuel Pump and Level Sensor Assembly
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 Control Module References
Special Tools
EL 35616-E - GM-Approved Terminal Test Kit Includes J 35616-200 Test Light Probe Kit
For equivalent regional tools, refer to Special Tools Tools and Equipment.
Circuit/System Testing
1. Ignition OFF, disconnect the harness connector at the appropriate fuel injector listed below:
* Q17A Fuel Injector 1
* Q17B Fuel Injector 2
* Q17C Fuel Injector 3
* Q17D Fuel Injector 4
2. Ignition ON, verify that a test lamp illuminates between the appropriate Q17 Fuel Injector ignition circuit terminal 1 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 Q17 Fuel Injector.
3. Ignition OFF, connect a J 35616-200 - Test Light Probe Kit between the K20 Engine Control Module control circuit terminal 2 and the ignition circuit terminal 1 of each Q17 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 K20 Engine Control Module control circuit for a short to ground. If the circuit tests normal, replace the K20 Engine Control Module.
• If the test lamp is always OFF, test the appropriate K20 Engine Control Module control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module.
5. If all circuits test normal, test or replace the appropriate Q17 Fuel Injector. Refer to Fuel Injector Diagnosis Fuel Injector Diagnosis.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Fuel Injector Replacement Service and Repair
* Control Module References Control Module References for ECM replacement, programming and setup