GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2005 🢒 XLR 🢒 Vehicle Control Systems 🢒 Vehicle DTC Information 🢒 Fuel Injector Solenoid Coil Test

Circuit Description

The control module enables the appropriate fuel injector pulse for each cylinder. 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 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
    • Excessive resistance in the fuel injector ignition 1 voltage circuit or the fuel injector control circuit may cause the following symptoms:
       - Lean condition
       - Misfire
       - Rough idle
    • Monitoring the misfire current counters, or misfire graph, may help 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 concern. A fuel injector condition may only be apparent at a certain temperature, or under certain conditions.

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 - Vehicle?

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Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2

Observe the ECT sensor parameter with a scan tool.

Is the ECT sensor parameter within the specified range?

10-32°C (50-90°F)

Go to Step 3

Go to Step 4

3
  1. Remove the fuel injector sight shield. Refer to Fuel Injector Sight Shield Replacement in Engine Mechanical - 4.6L (LH2).
  2. Measure the resistance of each fuel injector with a DMM. Refer to Testing for Continuity in Wiring Systems.

Do any of the fuel injectors display a resistance outside the specified range?

11-14 ohms

Go to Step 6

Go to Diagnostic Aids

4
  1. Remove the fuel injector sight shield. Refer to Fuel Injector Sight Shield Replacement in Engine Mechanical - 4.6L (LH2).
  2. Measure the resistance of each fuel injector with a DMM. Refer to Testing for Continuity in Wiring Systems.
  3. Record each fuel injector value.
  4. Subtract the lowest resistance value from the highest resistance value.

Is the difference equal to, or less than, the specified value?

3 ohms

Go to Fuel Injector Balance Test with Special Tool

Go to Step 5

5
  1. Add all of the fuel injector resistance values, to obtain a total resistance value.
  2. Divide the total resistance value by the number of fuel injectors, to obtain an average resistance value.
  3. Subtract the lowest individual fuel injector resistance value from the average resistance value.
  4. Compute the difference between the highest individual fuel injector resistance value and the average resistance value.
  5. Replace the fuel injector that displays the greatest resistance difference, above or below the average. Refer to Fuel Injector Replacement .

Did you complete the replacement?

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Go to Step 8

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6

Test for an intermittent and for a poor connection at the fuel injectors. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

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Go to Step 8

Go to Step 7

7

Replace the fuel injector or fuel injectors that are out of the specified range. Refer to Fuel Injector Replacement .

Did you complete the replacement?

11-14 ohms

Go to Step 8

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8

Operate the system in order to verify the repair.

Did you correct the condition?

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System OK

Go to Diagnostic Aids