GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2004 🢒 Grand Prix 🢒 Engine 🢒 Engine Electrical 🢒 Fuel Injector Circuit Diagnosis

Circuit Description

The control module enables the appropriate fuel injector on the intake stroke for each cylinder. The ignition relay supplies an ignition voltage to each fuel injector through an in-line mini-fuse. The control module controls each fuel injector by grounding the control circuit via a solid state device called a driver.

Diagnostic Aids
    • Monitoring the fuel injector circuit status with a scan tool while moving the fuel injector harness may help to isolate an intermittent condition.
    • Performing the Fuel Injector Coil Test may help isolate an intermittent condition. Refer to Fuel Injector Solenoid Coil Test .
    • For an intermittent condition, refer to Intermittent Conditions .

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. Test the ignition voltage supply circuit to the fuel injectors for a short to ground if the fuse is open.

    2.

  2. This step tests for a voltage on the ignition voltage supply circuit of the fuel injectors.

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

Connector End View Reference: Engine Controls Connector End Views or Powertrain Control Module Connector End Views

1

Did you perform the Diagnostic System Check-Engine Controls?

--

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

Inspect the fuel injector fuse.

Is the fuel injector fuse open?

--

Go to Step 5

Go to Step 3

3

Are any fuel injector DTCs set?

--

Go to DTC P0201, P0202, P0203, P0204, P0205, or P0206

Go to Step 4

4

  1. Turn OFF the ignition.
  2. Disconnect a fuel injector electrical connector.
  3. Turn ON the ignition.
  4. Probe the ignition voltage supply circuit of the fuel injector with a test lamp connected to a good ground.

Does the test lamp illuminate?

--

Go to Step 7

Go to Step 6

5
  1. Repair the short to ground in the ignition voltage supply circuit, between the fuel injector fuse and the fuel injectors. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
  2. Replace the fuse, if necessary.

Did you complete the repair?

--

Go to Step 8

--

6

Repair the open in the ignition voltage supply circuit, between the fuel injector fuse and the splice to the individual fuel injectors. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 8

--

7

Inspect for poor connections at the harness connectors of 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?

--

Go to Step 8

Go to Diagnostic Aids

8

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 2