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.

Circuit/System Description

The sequential fuel injection (SFI) system is controlled by the powertrain control module (PCM). Ignition voltage is supplied to the fuel injectors. The PCM controls each fuel injector by grounding the control circuit via a solid state device called a driver. When energized the fuel injector solenoid operates the solenoid plunger, allowing pressurized fuel to be injected into the intake port of the cylinder. The fuel pump will pressurize the fuel rail and the fuel injectors as long as the engine is cranking and the PCM is receiving the ignition system reference pulses.

Diagnostic Aids

* Monitoring the misfire current counters, or misfire graph, may help to isolate the fuel injector that is causing the condition.
* Operating the vehicle over a wide temperature range may help isolate the fuel injector that is causing the condition.
* If you were sent here by a DTC P0300 and all the injectors test normal, the Misfire Current Cylinder or Misfire Graphic information on a scan tool can be used to determine which injector circuit should be examined in detail.

Reference Information
Schematic Reference

Engine Controls Schematics ([1][2]Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Fuel System Description (Fuel System Description)
DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Powertrain Diagnostic Trouble Code (DTC) Type Definitions)
Scan Tool Reference

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

J 34730-2B Injector Test Lamp

Circuit/System Testing

Note:
* Perform this test for each fuel injector.
* If a cylinder specific misfire DTC was set, test the fuel injector of misfiring cylinder first.

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

• If the test lamp does not illuminate, test the ignition voltage circuit for a short to ground or an open/high resistance. If the circuit tests normal, test the IG2 ignition relay. Refer to Ignition Relay Diagnosis (Ignition Relay Diagnosis).

3. Ignition OFF, connect a J 34730-2B between the control circuit terminal 2 and the ignition 1 voltage circuit terminal 1.
4. Engine cranking or running, the injector test lamp should flash.

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

5. If all circuits test normal, test or replace the fuel injector.

Component Testing

1. Ignition OFF, disconnect the harness connector at the appropriate fuel injector.

Note: The engine coolant temperature (ECT) sensor must be between 19-21°C (64-72°F) in order for an accurate measurement.

2. Test for 11.4-12.6 ohm between the ignition voltage terminal 1 and the control terminal 2.

• If not within the specified range, replace the fuel injector.

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 powertrain control module replacement, setup, and programming