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. The fuel injector tester 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
• | 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
Special Tools
• | CH-48027 Digital Pressure Gauge |
• | EL-39021 Fuel Injector Coil and Balance Tester |
• | EL-44602 Injector Test Adapter |
For equivalent regional tools, refer to LINK 177833.
Component Testing
Static Test
Fuel Injector Coil Static Test
Verify the resistance of each fuel injector with one of the following methods:
• | If the engine coolant temperature (ECT) sensor is between 10°C to 32°C (50°F to 90°F), the resistance of each fuel injector should be 11 to 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 ECT sensor is not between 10°C to 32°C (50°F to 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 Fuel Pressure Test 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. |
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. |
- Install a fuel pressure gage. Refer to LINK (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 gage with the fuel pump relay commanded ON. The fuel pressure should be 345 to 414 kPa (50 to 60 PSI).
- Monitor the fuel pressure gauge for five minutes. The fuel pressure should not decrease more than 34 kPa (5 psi).
- Perform the Fuel Injector Balance Test
Fuel Injector Balance Test
- Set the selector switch on the fuel injector tester to the Balance Test 50 pulses/10 ms position.
- Connect the
EL-39021 Fuel Injector Coil and Balance Tester
to a fuel injector with a
EL-44602 Injector Test Adapter
.
- 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.
- Command the fuel pump relay ON one more time and energize the fuel injector by depressing the Activate Injector button on the
EL-39021 Fuel Injector Coil and Balance Tester
at the
previously selected pressure.
- 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.
- Clear the Min/Max results.
- Select Normal from the Display Mode.
- Repeat steps 2 and 4 through 7 for each fuel injector.
- Perform the Pressure Drop Calculation.
Pressure Drop Calculation
- 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 together. 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(s). |
Repair Instructions
Perform the
Diagnostic Repair Verification after completing the diagnostic procedure.
LINK (Fuel Injector Replacement)