G5 L4-2.2L (2007)
Fuel Injector: Testing and Inspection
Fuel Injector Diagnosis (w/J 39021 or Tech 2)
Fuel Injector Diagnosis (w/J39021 or w/Tech 2)
Diagnostic Fault Information
Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. See: Testing and Inspection/Initial Inspection and Diagnostic
Overview/Diagnostic Starting Point - Vehicle
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
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Monitoring the misfire current counters, or misfire graph, may help to isolate the fuel injector that is causing the condition.
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Operating the vehicle over a wide temperature range may help isolate the fuel injector that is causing the condition.
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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.
Component Testing
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).
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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.
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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.
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If the difference is equal to or less than 3 ohms, perform the Fuel Injector Balance Test-Fuel Pressure Test.
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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.
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Replace the fuel injector that displays the greatest resistance difference above or below the average.
5. Perform the Fuel Injector Balance Test-Fuel Pressure Test.
Important:
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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.
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Verify that adequate fuel is in the fuel tank before proceeding with this diagnostic.
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Before proceeding with this test review the User Manual CH 48027-5 for Safety Information and Instructions.
Fuel Injector Balance Test-Fuel Pressure Test
