Circuit Diagnosis - Fuel Injector

Circuit Description
The Powertrain Control Module (PCM) controls each individual fuel injector by providing a ground, this system is referred as Sequential Multiport Fuel Injection (SFI). When the ignition switch is turned to the on or start position (engine running), the PCM will energize/de-energize the fuel injector solenoid coil. With this coil energized, a plunger is activated, allowing pressurized fuel to be sprayed through the fuel injectors into the combustion chamber where it is mixed with air from the intake manifold; thus creating the proper air/fuel mixture needed for combustion.

Diagnostic Aids
Check for any of the following conditions:
^ Water, foreign material, or stale fuel can cause a no start or a hard start condition.
^ Erratic fuel pressure or a restricted fuel filter may cause a no start or a hard start condition.
^ Faulty fuel injectors. There may be fuel spray at the fuel injectors, but it may not be enough to start the engine. Normal fuel injector resistance is 12-17 ohms at 20°C (68°F). If the fuel injectors and their circuits are OK, and fuel spray is detected, the fuel injector nozzle may be partly blocked or restricted.

An intermittent malfunction may be caused by a poor connection, rubbed through wire insulation, or a wire broken inside the insulation. Inspect the wiring harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal-to-wire connections before component replacement.

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. If a fuse is found to be the cause of the no start, locate and repair any shorts that may have caused the fuse to blow before replacing the fuse.
4. After one minute from the time the fuel pump stops running the fuel pressure should drop and hold to approximately 180 kPa (25 psi).