Fuel Injector Diagnosis (CH47976)

Fuel Injector Diagnosis (CH47976)

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 provide an overview of each diagnostic category.

Circuit/System Description

The engine control module (ECM) enables the appropriate fuel injector pulse for each cylinder. The ignition voltage is supplied directly to the fuel injectors. The ECM controls each fuel injector by grounding the control circuit via a solid state device called a driver. A fuel injector coil winding resistance that is too high or too low will affect the engine driveability. A fuel injector control circuit DTC may not set, but a misfire may be apparent. The fuel injector coil windings are affected by temperature. The resistance of the fuel injector coil windings will increase as the temperature of the fuel injector increases.

The CH-47976 - Active Fuel Injector Tester , is used to test the fuel pump, fuel system leak down, and the fuel injectors. Following the User Guide, CH 47976-11, and the on screen prompts or selections, will indicate the steps required to perform each of the available tests. The tester will perform all of the tests automatically and display results of the test. The results can also be down loaded for storage and printing.

Diagnostic Aids

* Downloading the AFIT test results to the shop TIS terminal will clearly show which injector is at fault by the bar graph turning red.

* On some vehicles cleaning the injectors may be performed if the graph shows erratic or values close to the specified values.

* A second test can be performed to verify repair. Compare the first balance test to the second.

Reference Information

Schematic Reference

Engine Controls Schematics (except L96) [1][2]Electrical DiagramsEngine Controls Schematics (L96) [1][2]Electrical Diagrams

Connector End View Reference

Component Connector End Views 1-2 Shift Solenoid (SS) Valve (M30)

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

Special Tools

CH-47976 - Active Fuel Injector Tester

Component Testing

Fuel Injector Coil Test

Verify the resistance of each fuel injector:

1. Ignition ON, verify the scan tool ECT temperature is between 10-32°C (50-90° F).

• If not within the specified range, measure and record the resistance of each fuel injector with a DMM. Subtract the lowest resistance value from the highest resistance value. The difference between the lowest value and the highest value should be equal to or less than 3 ohms. If the difference is greater than 3 ohms, add all of the fuel injector resistance values to obtain a total resistance value. Divide the total resistance value by the number of injectors to obtain an average resistance value. Subtract the lowest individual fuel injector resistance value from the average resistance value. Subtract the average resistance value from the highest individual injector resistance value. Replace the fuel injector that displays the greatest difference above or below the average.

2. Test for 11-14 ohms between each fuel injector.

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

3. If all the injectors test OK, refer to the Active Fuel Injector Tester (AFIT) Procedure.

Active Fuel Injector Tester (AFIT) Procedure

Note:

* DO NOT perform this test if the engine coolant temperature (ECT) is above 94°C (201°F). Irregular fuel pressure readings may result due to hot soak fuel boiling.

* Verify that adequate fuel is in the fuel tank before proceeding with this diagnostic.

1. Verify the battery is fully charged and all accessories are OFF.

2. Ignition OFF.

3. Install the CH-47976 - Active Fuel Injector Tester. Refer to the AFIT User Guide.

4. Turn ON the AFIT and select the vehicle.

5. Follow the setup screen on the AFIT.

6. Ignition ON, perform the Injector Test. The test should run and pass all injectors.

• If the AFIT aborts testing due to fuel pressure or fuel leak down, refer to Fuel System Diagnosis (Without FPCM) Testing and InspectionFuel System Diagnosis (FPCM) Fuel System Diagnosis.

• If any injector exceeds the recommended tolerance, replace the injector(s), E-85 only. All other engines, refer to Fuel Injector Cleaning Procedures.

Repair Instructions

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

Fuel Injector Replacement Removal and Replacement