Fuel Injector Circuit Diagnosis

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.

TEST DESCRIPTION

Step 1 - Step 10:

Step 11 - Step 13:

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. This step checks for fuel injector control signals from the PCM.
3. This step checks for a fault that affects all the fuel injectors.
5. This step checks for a short in the fuel injector control circuit.
8. This step checks for ignition positive voltage.