GM Service Manual Online
For 1990-2009 cars only
Table 1: Example (Typical)
Table 2: Fuel Injector Coil Test Procedure - ECT Outside 10°C-35°C (50°F-95°)

Object Number: 17707  Size: MF

Test Description

Caution: Wrap a shop towel around the fuel pressure connection in order to reduce the risk of fire and personal injury. The towel will absorb any fuel leakage that occurs during the connection of the fuel pressure gage. Place the towel in an approved container when the connection of the fuel pressure gage is complete.

  1. The first second of the voltage displayed by the DMM may be inaccurate due to the initial current surge, therefore, record the lowest voltage displayed by the DMM after the first second of the test. The voltage displayed by the DMM may increase throughout the test as the fuel injector windings warm and the resistance of the fuel injector windings changes. Any large fluctuations in the voltage that do not stabilize indicate an intermittent connection within the fuel injector. From the voltages recorded, identify the highest voltage, excluding any voltages above 9.5 volts. Subtract each voltage that is not above 9.5 volts from the highest voltage. Record each subtracted value. The subtracted value for any fuel injector must not exceed 0.7 volt. A fuel injector with a subtracted value that is more than 0.7 volt is considered poor and must be replaced. A fuel injector with a recorded voltage of more than 9.5 volts is also considered poor and must be replaced.

Example (Typical)

Highest Voltage Reading

Acceptable Subtracted Value Above/Below

10°C-35°C (50°F-95°F)

7.1 Volts

0.7 Volts

Injector Number

Voltage

Subtracted Value

Pass/Fail

1

9.8

--

F

2

6.6

0.3

P

3

6.9

0.0

P

4

5.8

1.1

F

Fuel Injector Coil Test Procedure - ECT Outside 10°C-35°C (50°F-95°)

Step

Action

Value(s)

Yes

No

1

Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?

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Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2

Use a scan tool in order to observe the engine coolant temperature (ECT).

Is the ECT outside the specified range?

10°C-35°C (50°F-95°F)

Go to Step 3

Go to Fuel Injector Solenoid Coil Test - Engine Coolant Temperature Between 10-35 Degrees C (50-95 Degrees F)

3

  1. Turn off the ignition.
  2. Notice: In order to prevent flooding of a single cylinder and possible engine damage, relieve the fuel pressure before performing the fuel injector coil test procedure.

  3. Relieve the fuel pressure. Refer to Fuel Pressure Relief
  4. Access the fuel injector connectors as required.
  5. Connect the J 39021 Fuel Injector Tester to B+ and to ground.
  6. Set the amperage supply selector switch on the fuel injector tester to the Coil Test 0.5 amp position.
  7. Connect the leads from the digital multimeter (DMM) to the fuel injector tester.
  8. Set the DMM to the tenths scale (0.0).
  9. Connect the fuel injector tester to a fuel injector using the J 39021-380 Fuel Injector Test Harness.
  10. Important: Inspect the ECT again in order to ensure that the correct chart is being used.

  11. Press the Push to Start Test button on the fuel injector tester.
  12. Important : The voltage reading may rise during the test.

  13. Observe the voltage reading on the DMM.
  14. Record the lowest voltage observed after the first second of the test.
  15. Repeat steps 8 through 11 for each fuel injector.
  16. Identify the highest voltage reading recorded other than those more than 9.5 volts.
  17. Subtract any other voltage reading recorded from the highest voltage reading recorded. Refer to Example Table above.
  18. Repeat step 14 for all of the remaining fuel injectors.

Is any difference more than the specified value?

0.7 V

Go to Step 4

Go to Fuel Injector Balance Test

4

Replace any fuel injector that had any of the following conditions :

    • A subtracted value exceeding 0.7 volts.
    • An initial reading of more than 9.5 volts.
    • An erratic reading.

Refer to Fuel Injector Replacement

Did you complete the repair?

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Go to Fuel Injector Balance Test

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