GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2007 🢒 Vibe - FWD 🢒 Engine 🢒 Engine Controls and Fuel - 1.8L (LV6) 🢒 Fuel Injector Circuit Diagnosis

Circuit Description

The sequential multiport fuel injection (SFI) system is controlled by the powertrain control module (PCM). The PCM energizes the solenoid coil of each fuel injector individually by completing the electrical circuit to ground. When energized the fuel injector solenoid operates the solenoid plunger, allowing pressurized fuel to be injected into the intake port of the cylinder. The fuel pump will pressurize the fuel rail and the fuel injectors as long as the engine is cranking and the PCM is receiving the ignition system reference pulses.

Diagnostic Aids

Check for any of the following conditions:

    • Water, contaminated fuel, or inferior quality fuel can cause a no start or hard start condition even though the fuel injectors and circuitry are OK.
    • Check for a faulty spray pattern from the fuel injector nozzle if both the fuel injector solenoid and the fuel injector circuit are OK.
    • There may be fuel spray at the fuel injectors and the indicated fuel pressure may be correct, yet there may not be enough fuel to start the engine. If the fuel injectors and the injectors' circuit are OK, and fuel spray is detected, some fuel injector nozzles may be partly blocked or restricted. If the PCM receives incorrect inputs from the various information sensors the fuel delivered by the fuel injectors may be inadequate to start the engine. Check all engine data parameters with a scan tool and compare the values indicated with expected values or values on a known good vehicle.
    • The normal fuel injector resistance is 13.4-14.4 ohms at 20°C (68°F).
    • If you were sent here by a DTC P0300 and all the injectors checked OK, the Misfire Current Cylinder or Misfire Graphic information on a scan tool can be used to determine which injector circuit should be examined in detail.

An intermittent malfunction may be caused by a fault in the fuel injector electrical circuit. Inspect the wiring harness and the components for an intermittent condition. Refer to Intermittent Conditions .

Test Description

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

  1. The Diagnostic System Check - Vehicle prompts the technician to complete some basic checks and store the Freeze Frame data on the scan tool, if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.

    2.

  2. This step checks for fuel injector control signals from the PCM.

    3.

  3. This step checks for a fault that affects all the fuel injectors.

    4.

  4. This step checks for a short in the fuel injector control circuit.

    5.

  5. This step checks for ignition positive voltage.

Step

Action

Yes

No

Schematic Reference: Engine Controls Schematics

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

Important: This table assumes that the malfunction indicator lamp (MIL) and the data link connector (DLC) function normally. Verify that the MIL operation and the DLC communication are OK before using this table.

  1. Turn OFF the ignition.
  2. Disconnect all 4 fuel injector electrical connectors.
  3. Install a fuel injector test lamp into each fuel injector harness connector.
  4. Observe the injector test lamp for each injector while cranking the engine.

Does the injector test lamp flash for each injector circuit while cranking the engine?

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

Go to Step 3

3

Did the fuel injector test lamp flash for at least one fuel injector circuit while cranking the engine?

Go to Step 5

Go to Step 4

4
  1. Check for any of the following conditions:
    2. • An open in the fuel injector power circuit between the ignition switch and S114.
    • An open in the powertrain control module (PCM) ground circuits.
  2. Repair as necessary. Refer to Wiring Repairs .

Is the action complete?

Go to Step 12

--

5

Was the injector test lamp illuminated steady for any fuel injector circuit?

Go to Step 6

Go to Step 8

6
  1. Turn OFF the ignition.
  2. Install the fuel injector test lamp in any fuel injector circuit that stays ON.
  3. Disconnect PCM electrical connector C1.
  4. Turn ON the ignition, with the engine OFF.

Does the fuel injector test lamp illuminate?

Go to Step 7

Go to Step 11

7

Repair the short to ground in the faulty fuel injector control circuit between the PCM and the fuel injector. Refer to Wiring Repairs .

Is the action complete?

Go to Step 12

--

8

  1. Remove the injector test lamp from the fuel injector electrical connector.
  2. Connect a test lamp from ground to the ignition positive voltage side of the fuel injector harness connector that did not flash.
  3. Turn ON the ignition, with the engine OFF.

Does the test lamp illuminate?

Go to Step 10

Go to Step 9

9

Repair the open in the ignition feed circuit between the fuel injector and S114. Refer to Wiring Repairs .

Is the action complete?

Go to Step 12

--

10
  1. Check for an open in the faulty fuel injector control circuit.
  2. Repair as necessary. Refer to Wiring Repairs .
  3. Repeat Step 5 through Step 10 until the injector test lamp flashes in all 4 fuel injector circuits.

Was a repair necessary?

Go to Step 12

Go to Step 11

11

Replace the PCM. Refer to Control Module References for replacement, setup, and programming.

Is the action complete?

Go to Step 12

--

12
  1. Use the scan tool in order to clear the DTCs.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the conditions that caused the concern.

Does the fuel system now operate properly?

Go to Step 13

Go to Diagnostic Aids

13

With a scan tool, observe the stored information, Capture Info.

Does the scan tool display any DTCs that you have not diagnosed?

Go to Diagnostic Trouble Code (DTC) List - Vehicle

System OK