GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2000 🢒 Grand Prix 🢒 Engine 🢒 Engine Controls - 3.1L (LG8) 🢒 Fuel Injector Solenoid Coil Test - Engine Coolant Temperature Outside 10-35 Degrees C (50-95 Degrees F)
Table 1: Example
Table 2: Fuel Injector Coil Test -- ECT outside 10°C-35°C (50°F-95°F)

Circuit Description

The PCM controls the fuel injector control circuit using a Multi Function Driver (MFD). Power is supplied by the injector fuse to the injector and is grounded by the PCM. The MFD controls the injector ground, allowing fuel flow to pulse.

Diagnostic Aids

Test the engine fuel injection harness for the following conditions:

    • Poor terminal connection.
        Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged and faulty terminal to wire connections. Use a corresponding mating terminal to test for proper tension. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
    • Damaged harness.
        Inspect the wiring harness for damage. Refer to Wiring Repairs in Wiring Systems.

Test Description

Numbers below refer to the step numbers on the Diagnostic Table.

  1. The engine coolant temperature affects the resistance in the fuel injector and the ability of the fuel injector tester to detect a faulty fuel injector. If the engine coolant temperature is between the specified value, go to Fuel Injection Coil Test - ECT Between 10°C-35°C.

    2.

  2. The first second of the voltage displayed by the digital multimeter (DMM) may be inaccurate due to the initial current surge. Therefore, record the lowest voltage displayed by the DMM after the first second. 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 change. An erratic voltage reading (large fluctuations in voltage that does not stabilize indicates an intermittent connection within the fuel injector. From the voltages recorded, identify the highest voltage, excluding any voltages above 9.5 volts. A fuel injector with a recorded voltage above 9.5 volts is also considered faulty and must be replaced.

    3.

  3. Subtract each voltage from the highest recorded voltage below 9.5 volts. Record each subtracted value (refer to the Example). The subtracted value for any fuel injector must not exceed 0.6 volt. A fuel injector with a subtracted value that is greater than the specified value is considered faulty and must be replaced.

Example

Highest Voltage Reading

Acceptable Subtracted Value Above/Below

10°C-35°C

(50°F-95°F)

7.1 Volts

0.6 Volts

Injector Number

Voltage

Subtracted Value

Pass/Fail

1

9.8

F

2

6.6

0.5

P

3

6.9

0.2

P

4

5.8

1.3

F

5

7.0

0.1

P

6

7.1

0.0

P

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

Step

Action

Value(s)

Yes

No

1

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

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2

  1. Turn ON the ignition, with the engine OFF.
  2. With a scan tool, monitor the ECT parameter.

Does the temperature measure outside the specified value?

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

Important : Fuel system must not be pressurized. Refer to Fuel Pressure Relief .

  1. Install the J 39021 Fuel Injector Coil/Balance Tester, J 39021 - 210 Injector Selector Switch Box and the J 39021-410 Fuel Injection Coil Test harness.
  2. Select the coil test 0.5 AMP position on the fuel injector tester.
  3. Connect the leads of the digital multimeter (DMM) to the fuel injector tester and select DC voltage tenths scale.
  4. Select an injector on the J 39021 - 210 Injector Selector Switch Box.
  5. Press the PUSH TO START TEST button on the Fuel Injector Coil/Balance Tester.
  6. Record the lowest reading after the first second.
  7. Repeat for each fuel injector.

Does any fuel injector have an erratic reading or a reading above the specified value?

9.5 volts

Go to Step  5

Go to Step  4

4

  1. From the recorded readings, identify the highest voltage.
  2. Subtract all other voltage readings from the highest voltage recorded.

Does any subtracted value exceed the specified value?

.6 volts

Go to Step 5

Go to Fuel Injector Balance Test

5
  1. Remove the upper Intake manifold. Refer to Intake Manifold Replacement in Engine Mechanical.
  2. Test the fuel injection harness between the 16-way connector and the injector for the following conditions:
    3. • An open or short to ground in the fuel injection harness.
    • Poor terminal connections at the fuel injector.

Did you find and correct the condition?

--

Go to Step 7

Go to Step 6

6

Replace the faulty fuel injectors. Refer to Fuel Injector Replacement

Did you complete the replacement?

--

Go to Step 7

--

7

Does any driveabilty condition still exist?

--

Go to Applicable Diagnostic

System OK