Fuel Injector Diagnosis (J39021 or Scan Tool)
Fuel Injector Diagnosis (J39021 or Scan Tool)
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.
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 [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
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
For equivalent regional tools, refer to Special Tools Tools and Equipment
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 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 then 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 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 fuel 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 Fuel Injector Balance Test-Fuel Pressure Test.
Fuel Injector Balance Test-Fuel Pressure Test
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.
1. Install a CH-48027 - pressure gauge. Refer to Fuel Pressure Gauge Installation and Removal Fuel Pressure Gauge Installation and Removal.
2. Ignition ON, engine OFF.
Note:
* 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 fuel pressure gauge with the fuel pump commanded ON. The fuel pressure should be 345-414 kPa (50-60 psi).
• If not within the specified range, refer to Fuel System Diagnosis Fuel System Diagnosis.
5. Monitor the CH-48027 - pressure gauge for one minute. The fuel pressure should not decrease greater than 34 kPa (5 psi).
• If greater than the specified range, refer to Fuel System Diagnosis Fuel System Diagnosis.
6. Perform the Fuel Injector Balance Test with Special Tool or the Fuel Injector Balance Test with Scan Tool.
Fuel Injector Balance Test with Special Tool
1. Install a CH-48027 - pressure gauge. Refer to Fuel Pressure Gauge Installation and Removal Fuel Pressure Gauge Installation and Removal.
2. Set the amperage supply selector switch on the J-39021 - fuel injector coil and balance tester to 0.5-2.5 amp position.
3. Connect the J-39021 - fuel injector coil and balance tester to a fuel injector with a J-44602 - test adapter.
4. Command the Fuel Pump Relay ON 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.
5. Command the Fuel Pump Relay 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.
6. After the injector stops pulsing, select Min from the Display Mode on the CH-48027 - 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 - pressure gauge.
8. Select Normal from the Display Mode on the CH-48027 - pressure gauge.
9. Repeat steps 2 and 4 through 7 for each fuel injector.
10. Perform the Pressure Drop Calculation.
Fuel Injector Balance Test with Scan Tool
1. Command the Fuel Pump Relay ON 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. Select the Fuel Injector Balance Test with a scan tool.
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 - 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 - pressure gauge.
8. Select Normal from the Display Mode on the CH-48027 - 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 greater than the specified value, 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 (Petrol) Removal and Replacement