Circuit Description
The engine control module (ECM) enables the appropriate fuel injector on the intake stroke for each cylinder. 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 low, will affect 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.
Diagnostic Aids
Injector | 1 | 2 | 3 | 4 | 5 | 6 |
|---|---|---|---|---|---|---|
Measured resistance of each fuel injector | 12 ohms | 13 ohms | 13.5 ohms | 14 ohms | 10 ohms | 12 ohms |
Lowest resistance value subtracted from the highest resistance value | Injector 4 = 14 ohms Injector 5 = 10 ohms =4 ohms | -- | -- | -- | -- | -- |
Sum of all fuel injector resistance values divided by the total number of fuel injectors | Injector 1 = 12 ohms Injector 2 = 13 ohms Injector 3 = 13.5 ohms Injector 4 = 14 ohms Injector 5 = 10 ohms Injector 6 = 12 ohms = 74.5 ohms Average resistance value: 74.5 /6 = 12.4 ohms | -- | -- | -- | -- | -- |
Subtract the lowest injector resistance value from the average resistance value | Average resistance value = 12.4 ohms Injector 5 = 10 ohms Difference = 2.4 ohms | -- | -- | -- | -- | -- |
Compute the difference between the highest injector resistance value and the average resistance value Subtract the average resistance value from the highest injector resistance value. | Injector 4 = 14 ohms Average resistance value = 12.4 ohms Difference = 1.6 ohms Replace fuel injector 5. | -- | -- | -- | -- | -- |
| • | 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. |
| • | If the fuel injector coil test does not isolate the condition perform the fuel injector balance test. Refer to Fuel Injector Balance Test with Special Tool . |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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This step tests each fuel injector resistance within a specific temperature range.
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This step determines if all of the fuel injectors are within 3 ohms of each other. If the highest resistance value is within 3 ohms of the lowest resistance value, then all of the fuel injector coil windings are OK.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Control Module Connector End Views or Engine Controls Connector End Views | ||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |
2 | Observe the engine coolant temperature (ECT) with a scan tool. Is the ECT parameter above the specified value? | 20°C (68°F) | Go to Step 3 | Go to Step 4 |
Do any of the fuel injectors display a resistance outside the specified range? | 13-15.5 ohms | Go to Step 6 | Go to Diagnostic Aids | |
Is the difference equal to, or less than, the specified value? | 3 ohms | Go to Step 5 | ||
5 |
Did you complete the replacement? | -- | Go to Step 7 | -- |
6 | Replace the fuel injector or fuel injectors that are out of the specified range. Refer to Fuel Injector Replacement and Fuel Injector and Fuel Rail Replacement . Did you complete the replacement? | 13-15.5 ohms | Go to Step 7 | -- |
7 | Operate the system in order to verify the repair. Did you correct the condition? | -- | System OK | |
