Fuel Injector Circuit Diagnosis

Circuit Description
The powertrain control module (PCM) energizes the solenoid coil of the fuel injector. When energized the fuel injector solenoid operates the solenoid plunger allowing pressurized fuel to be injected into the bore of the throttle body fuel injection unit. The fuel pump will pressurize the fuel injector as long as the engine is cranking, and the PCM is receiving ignition system reference pulses. The fuel pump will stop after 2 seconds if the PCM does not receive any ignition system reference pulses.

Diagnostic Aids
Check for a faulty fuel injector. There may be fuel spray at the fuel injector, but it may not be enough to start the engine. Normal fuel injector resistance is 0.5-1.5 ohms at 20°C (68°F). Check for a partially blocked fuel injector nozzle if both the fuel injector solenoid and the fuel injector circuit are OK.

Check the fuel injector resistor for faulty electrical connections or high electrical resistance. Normal fuel injector resistor resistance is 1.9-2.8 ohms at 20°C (68°F).

An intermittent malfunction may be caused by a fault in the fuel injector electrical circuit. Inspect the wiring harness and components for any of the following conditions:
^ Backed out terminals.
^ Improper mating of terminals.
^ Broken electrical connector locks.
^ Improperly formed or damaged terminals.
^ Faulty terminal to wiring connections.
^ Physical damage to the wiring harness.
^ Broken conductor inside the wire insulation.
^ Corrosion of electrical connections, splices, or terminals.

Test Description
The numbers below refer to the step numbers in the Diagnostic Table.
1. The Powertrain OBD System Check 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 if the PCM is controlling the fuel injector signals.
3. This step checks the fuel injector for the correct resistance.
5. This step checks for voltage at the fuel injector.
6. This step checks for an open or a short to ground in fuel injector control circuit, for a faulty PCM, or for a faulty fuel injector.
13. This step checks for an open in the YEL wire, an open in the ignition feed circuit or for a faulty fuel injector resistor.