Fuel Injector Diagnosis (J 39021 or Tech 2)
Fuel Injector Diagnosis (J 39021 or Tech 2)
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 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.
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.
* Perform the fuel injector coil test within the conditions of the customer's concern. A fuel injector condition may only be apparent at a certain temperature, or under certain conditions.
Reference Information
Schematic Reference
Engine Controls Schematics (LZ1) [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
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References Control Module References for scan tool information
Special Tools
* CH-48027 - Digital Pressure Gauge
* J 39021 - Fuel Injector Coil and Balance Tester
* J 44602 - Injector Test Adapter
Component Testing
Fuel Injector Coil Test
1. Ignition OFF, open the hood to disable the Auto-Stop function. Refer to Hybrid Modes of Operation Description Hybrid Modes of Operation Description.
2. Ignition ON, verify the scan tool hood position parameter displays Open.
• If the hood position does not display Open, refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle for DTC P254F.
3. Verify the resistance of each fuel injector with one of the following methods:
* If the engine coolant temperature (ECT) sensor is between 10-32°C (50-90°F), the resistance of each fuel injector should be 11-14 ohms.
• If the injectors measure OK, perform the Fuel Injector Balance Test - Fuel Pressure Test.
• If not within the specified range, replace the fuel injector.
* If the ECT sensor is not between 10-32°C (50-90°F), 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, refer to Fuel Injector Balance Test - Fuel Pressure Test for further diagnosis of the fuel injectors.
• 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 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 difference above or below the average.
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.
* Before proceeding with this test review the User Manual CH 48027-5 for Safety Information and Instructions.
Fuel Injector Balance Test-Fuel Pressure Test
1. Ignition OFF, install a CH-48027 - fuel pressure gauge. Refer to Fuel Pressure Gauge Installation and Removal Testing and Inspection.
Note:
* The fuel pump Enable may need to be commanded ON a few times in order to obtain the highest possible fuel pressure.
* DO NOT start the engine.
2. Ignition ON, command the fuel pump Enable ON with a scan tool. Verify the fuel pressure is within 365-414 kPa (53-60 psi).
• If not within the specified range, refer to Fuel System Diagnosis Fuel System Diagnosis for further diagnosis of the fuel system.
3. Monitor the CH-48027 - fuel pressure gauge for one minute. The fuel pressure should not decrease greater than 34 kPa (5 psi).
• If the fuel pressure decreases greater than 34 kPa (5 psi), refer to Fuel System Diagnosis Fuel System Diagnosis.
4. 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 - fuel injector coil and balance tester to a fuel injector with a J 44602 - injector test adapter.
3. Command the fuel pump Enable ON and then OFF three times with a scan tool. On the last command, as the fuel pressure begins to slowly degrade and stabilize, select a fuel pressure within 34 kPa (5 psi) of the maximum pump pressure. Record this fuel pressure. This is the starting pressure at which you will pulse each injector.
4. Command the fuel pump Enable ON one more time and energize the fuel injector by depressing the Push to Start Test button on the J 39021 - fuel injector coil and balance tester at the previously selected pressure.
5. After the injector stops pulsing, select Min from the Display Mode and record the Min pressure.
Note: New test results will not be recorded if the Min/Max results are not cleared after each injector is tested.
6. Clear the Min/Max results.
7. Select Normal from the Display Mode.
8. Repeat steps 2 and 4 through 7 for each fuel injector.
9. Perform the Pressure Drop Calculation.
Fuel Injector Balance Test with Tech 2
1. Command the fuel pump Enable ON and then OFF three times with a scan tool. On the last command, as the fuel pressure begins to slowly degrade and stabilize, select a fuel pressure within 34 kPa (5 psi) of the maximum pump pressure. Record this fuel pressure. This is the starting pressure at which you will pulse each injector.
2. With a scan tool, select the Fuel Injector Balance Test function within the Special Functions menu.
3. Select an injector to be tested.
4. Press Enter to prime the fuel system.
5. Energize the fuel injector by depressing the Pulse Injector button on the scan tool at the previously selected pressure.
6. After the injector stops pulsing, select Min from the Display Mode on the CH-48027 - fuel pressure gauge and record the Min pressure.
Note: New test results will not be recorded if the Min/Max results are not cleared after each injector is tested.
7. Clear the Min/Max results on the CH-48027 - fuel pressure gauge.
8. Select Normal from the Display Mode on the CH-48027 - fuel pressure gauge.
9. Press Enter on the scan tool to bring you back to the Select Injector screen.
10. Repeat steps 3 through 9 for each fuel injector.
11. Perform the Pressure Drop Calculation.
Pressure Drop Calculation
1. Subtract the minimum pressure from the starting pressure 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 except for the injector suspected of being faulty. This is the total pressure drop.
4. Divide the total pressure drop by the number of fuel injectors that were added together. This is the average pressure drop. The difference between any individual pressure drop and the average pressure drop should not be greater 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, E-85 only. All other engine, 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