Always perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

The control module enables the appropriate fuel injector pulse for each cylinder. The ignition voltage is supplied directly to the fuel injectors. The control module 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.

When performing the fuel injector balance test, the scan tool is first used to energize the fuel pump relay. The fuel injector tester or the scan tool is then used to pulse each injector for a precise amount of time, allowing a measured amount of the fuel to be injected. This causes a drop in the system fuel pressure that can be recorded and used to compare each injector.

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Electrical Information Reference

Scan Tool Reference

Special Tools Required

Fuel Injector Coil Test

1. Observe the ECT Sensor parameter with a scan tool. The ECT sensor should be 10-32°C (50-90°F).

⇒	If the ECT Sensor parameter is not within 10-32°C (50-90°F), go to step 3.

2. Measure the resistance of each fuel injector with a DMM. The resistance of each fuel injector should be 11-14 ohms.

⇒	If the resistance of any fuel injector is not 11-14 ohms, replace the fuel injector.

3. 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 equal to or less than 3 ohms, perform the Fuel Injector Balance Test-Fuel Pressure Test.

⇒	If the difference is more than 3 ohms, continue with the Fuel Injector Coil Test.

4. Add all of the fuel injector resistance values to obtain a total resistance value. Divide the total resistance value by the number of fuel injectors to obtain an average resistance value. Subtract the lowest individual fuel injector resistance value from the average resistance value. Compute the difference between the highest individual fuel injector resistance value and the average resistance value.

⇒	Replace the fuel injector that displays the greatest resistance difference above or below the average.

5. If no fuel injectors were replaced, perform the Fuel Injector Balance Test-Fuel Pressure Test.

Important: 

Fuel Injector Balance Test-Fuel Pressure Test

1. Install a J 34730-1A . Refer to Fuel Pressure Gage Installation and Removal .
2. Turn ON the ignition, with the engine OFF.

Important: 

•	The fuel pump relay may need to be commanded ON a few times in order to obtain the highest possible fuel pressure.

•	DO NOT start the engine.

3. Command the fuel pump relay ON with a scan tool.
4. Observe the J 34730-1A with the fuel pump commanded ON. The fuel pressure should be 384-425 kPa (55-61 psi).

⇒	If the fuel pressure is not 384-425 kPa (55-61 psi), refer to Fuel System Diagnosis .

Important: The fuel pressure may vary slightly when the fuel pump stops operating. After the fuel pump stops operating, the fuel pressure should stabilize and remain constant.

5. Monitor the J 34730-1A for one minute. The fuel pressure should not decrease more than 34 kPa (5 psi).

⇒	If the fuel pressure decreases more than 34 kPa (5 psi), refer to Fuel System Diagnosis .

6. If a condition was not found, perform the Fuel Injector Balance Test with Special Tool or the Fuel Injector Balance Test with Tech 2.

Fuel Injector Balance Test with Special Tool

1. Set the amperage supply selector switch on the fuel injector tester to the Balance Test 0.5-2.5 amp position.
2. Connect the J 39021 and J 44602 to the fuel injector connector one at a time.
3. Command the fuel pump relay ON and then OFF with a scan tool.
4. Record the fuel pressure indicated by the J 34730-1A after the fuel pressure stabilizes. This is the first pressure reading.

Important: The fuel pressure may rise after the fuel injector stops pulsing. Record the fuel pressure value immediately after the fuel injector stops pulsing. DO NOT record the higher fuel pressure value.

5. Energize the fuel injector by depressing the Push to Start Test button on the fuel injector tester.
6. Record the fuel pressure indicated by the J 34730-1A after the fuel injector has stopped pulsing. This is the second pressure reading.
7. Repeat steps 2-6 for each fuel injector.
8. Perform the Pressure Drop Calculation.

Fuel Injector Balance Test with Tech 2

1. With a scan tool, select the Fuel Injector Balance Test function within the Special Functions menu.
2. Select an injector to be tested.
3. Press Enter to prime the fuel system.
4. Record the fuel pressure indicated by the J 34730-1A after the fuel pressure stabilizes. This is the first pressure reading.

Important: Record the fuel pressure value immediately after the fuel injector stops pulsing. The fuel pressure may rise after the fuel injector stops pulsing. DO NOT record the higher fuel pressure value.

5. Energize the fuel injector by depressing the Pulse Injector button on the scan tool. This will energize the injector and decrease the fuel pressure.
6. Record the fuel pressure indicated by the J 34730-1A after the fuel injector has stopped pulsing. This is the second pressure reading.
7. Press Enter again to bring you back to the Select Injector screen.
8. Repeat steps 2-7 for each fuel injector.
9. Perform the Pressure Drop Calculation.

Pressure Drop Calculation

1. Subtract the second pressure reading from the first pressure reading for one fuel injector. The result is the pressure drop value.
2. Obtain a pressure drop value for each fuel injector.
3. Add all of the individual pressure drop values. This is the total pressure drop.
4. Divide the total pressure drop by the number of fuel injectors. This is the average pressure drop. The difference between any individual pressure drop and the average pressure drop should not be more than 20 kPa (3 psi).

⇒	If the difference between any individual pressure drop and the average pressure drop is more than 20 kPa (3 psi), replace the fuel injector.

Important: Always perform the Diagnostic Repair Verification after completing the diagnostic procedure.