GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Epica 🢒 Engine 🢒 Engine Electrical 🢒 Fuel Injector Solenoid Coil Test

Circuit Description

The engine control module (ECM) enables the appropriate fuel injector pulse for each cylinder. Ignition 1 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 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
    • 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.

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?

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Go to Step 2

Go to Diagnostic System Check - Engine Controls

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. Turn OFF the ignition.

    2. Important: The multi-way harness connectors, C118 and C119, are located under the intake manifold in front of the engine.

  2. Disconnect the fuel injector multi-way harness connectors.
  3. On the injector side of the multi-way connectors, measure the resistance from the #1 fuel injector control circuit to the fuel injector ignition 1 voltage circuit with a DMM. Refer to Testing for Continuity in Wiring Systems.
  4. Record the fuel injector resistance value.
  5. Repeat step 3 and step 4 for the other fuel injectors.

Is the resistance within the specified range for each injector?

13-16 ohms

Go to Fuel Injector Balance Test with Special Tool

Go to Step 6

4
  1. Turn OFF the ignition.

    2. Important: The multi-way harness connectors, C118 and C119, are located under the intake manifold in front of the engine.

  2. Disconnect the fuel injector multi-way harness connectors.
  3. On the injector side of the multi-way connectors, measure the resistance from the #1 fuel injector control circuit to the fuel injector ignition 1 voltage circuit with a DMM. Refer to Testing for Continuity in Wiring Systems.
  4. Record the fuel injector resistance value.
  5. Repeat step 3 and step 4 for the other fuel injectors.
  6. 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 Injection Fuel Rail Assembly Replacement .

Did you complete the replacement?

--

Go to Step 8

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6

Test the fuel injector control circuit or control circuits for a high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

 

Go to Step 8

Go to Step 7

7

Replace the fuel injector or fuel injectors with resistance that is out of the specified range. Refer to Fuel Injection Fuel Rail Assembly Replacement .

Did you complete the replacement?

13-16 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 Step 2