Tahoe 2WD V8-6.0L Hybrid (2008)
Fuel Injector: Testing and Inspection
Fuel Injector Diagnosis (w/J 39021 or Tech 2)
Fuel Injector Diagnosis (w/J 39021 or Tech 2)
Diagnostic Instructions
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Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. See: Testing and Inspection/Initial Inspection and
Diagnostic Overview/Diagnostic System Check - Vehicle
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Review Strategy Based Diagnosis for an overview of the diagnostic approach.
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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
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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.
Special Tools
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CH-48027 Digital Pressure Gage
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J 39021 Fuel Injector Coil and Balance Tester
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J 44602 Injector Test Adapter
Component Testing
Fuel Injector Coil Test
Verify the resistance of each fuel injector with one of the following methods:
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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.
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If the injectors measure OK, perform the Fuel Injector Balance Test - Fuel Pressure Test.
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If not within the specified range, replace the fuel injector.
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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.
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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.
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If the difference is more 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.
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.
