Fuel Injector Diagnosis with Scan Tool
Diagnostic Instructions
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
Connector End View Reference
Component Connector End Views
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Special Tools
CH-48027 Digital Pressure Gage
For equivalent regional tools, refer to
Special Tools.
Component Testing
Fuel Injector Coil Static Test
Verify the resistance of each fuel injector with one of the following methods:
| • | If the B34A Engine Coolant Temperature (ECT) Sensor is between 10-32°C (50-90°F), the resistance of each fuel injector should be 11-14 Ω. |
| ⇒ | 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 B34A Engine Coolant Temperature (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 result obtained should be equal to or less than 3 Ω. |
| ⇒ | the difference is equal to or less than 3 Ω, refer to fuel injector balance test - fuel pressure test for further diagnosis of the fuel injectors. |
| ⇒ | If the difference is more than 3 Ω, add up 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. |
Fuel Injector Balance Test-Fuel Pressure Static 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 an adequate amount of fuel is in the fuel tank before proceeding with this diagnostic. |
| • | Before proceeding with this test review the
CH 48027 User Manual
for Safety Information and Instructions. |
- Install a fuel pressure gauge. Refer to
Fuel Pressure Gage Installation and Removal.
- Turn ON the ignition, with the 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. |
- Command the fuel pump relay ON with a scan tool.
- Observe the fuel pressure gauge with the fuel pump commanded ON. The fuel pressure should be 345-414 kPa (50-60 PSI).
- Monitor the fuel pressure gauge for 1 min. The fuel pressure should not decrease more than 34 kPa (5 PSI).
- Perform the Fuel Injector Balance Test with scan tool.
Fuel Injector Balance Test with Scan Tool Static Test
- Command the fuel pump relay 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.
- With a scan tool, select the fuel injector balance test function within the special functions menu.
- Select an injector to be tested.
- Press Enter to prime the fuel system.
- Energize the fuel injector by depressing the pulse injector button on the scan tool at the previously selected pressure.
- After the injector stops pulsing, select min from the display mode on the
CH-48027 Digital Pressure Gage
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.
- Clear the Min/Max results on the
CH-48027 Digital Pressure Gage
.
- Select normal from the display mode on the
CH-48027 Digital Pressure Gage
.
- Press enter on the scan tool to bring you back to the select injector screen.
- Repeat steps 3 through 9 for each fuel injector.
- Perform the pressure drop calculation.
Pressure Drop Calculation Static Test
- Subtract the minimum pressure from the starting pressure for one fuel injector. The result is the pressure drop value.
- Obtain a pressure drop value for each fuel injector.
- Add all of the individual pressure drop values except for the injector suspected of being faulty. This is the total pressure drop.
- Divide the total pressure drop by the number of fuel injectors that were added up. 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. |
Repair Instructions
Perform the
Diagnostic Repair Verification after completing the diagnostic procedure.
Fuel Injector Replacement
Fuel Injector Diagnosis with Special Tool
Diagnostic Instructions
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.
The active fuel injector tester
SA9182E Electronic Fuel Injector Tester
is used to test the fuel pump, fuel system leak down, and the fuel injectors. Following the user guide, 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 the results of the test. The results can also be downloaded for storage and printing.
Reference Information
Schematic Reference
Engine Controls Schematics
Connector End View Reference
Component Connector End Views
Electrical Information Reference
Special Tools
SA9182E Electronic Fuel Injector Tester
For equivalent regional tools, refer to
Special Tools.
Component Testing
Fuel Injector Coil Static Test
Verify the resistance of each fuel injector with one of the following methods:
| • | If the B34A Engine Coolant Temperature (ECT) Sensor is between 10°C-32°C (50°F-90°F), the resistance of each fuel injector should be 11-14 Ω. |
| ⇒ | If the injectors measure OK, perform the active fuel injector tester test procedure. |
| ⇒ | If not within the specified range, replace the LINK fuel injector replacement. |
| • | If the B34A Engine Coolant Temperature (ECT) Sensor is not between 10°C-32°C (50°F-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 two should be equal to or less than 3 Ω. |
| ⇒ | If the difference is equal to or less than 3 Ω, refer to active fuel injector tester test procedure for further diagnosis of the fuel injectors. |
| ⇒ | If the difference is more than 3 Ω, 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. |
Active Fuel Injector Tester Static Test 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. |
- Turn OFF all accessories.
- Turn OFF the ignition.
- Install the active fuel injector tester. Refer to the active fuel injector tester user guide.
- Turn ON the active fuel injector tester and select the vehicle.
- Turn ON the ignition and perform the injector test.
| ⇒ | If the active fuel injector tester aborts testing due to fuel pressure or fuel leak down, refer to
Fuel System Diagnosis. |
- View the test results.
| ⇒ | If any injector exceeds the recommended tolerance, replace the injector(s). |
Repair Instructions
Perform the
Diagnostic Repair Verification after completing the diagnostic procedure.
LINK (Fuel Injector Replacement)
