Diagnostic Overview-Fuel Injector

PCM DIAGNOSTIC OVERVIEW: The Powertrain Control Module (PCM) monitors the inductive voltage spike, or fly back voltage created by the collapse of the magnetic field in the injector coil. This allows the Battery supply circuit, injector coil and control circuit to be monitored for electrical faults.

The wiring and components can be tested individually, or the entire system can be tested using a multi-channel scope. Regardless of the chosen test method, the following checks should be performed during diagnostics:

Verify that the Battery supply to the Fuel Injector is present and is capable of operating a load.
Verify the control circuit is not open or shorted to ground.
Verify that the Fuel Injector coil is not open or shorted across the coil. Low resistance in the Fuel Injector coil will cause excessive current draw causing the PCM to turn off the driver for self-protection.
Verify that the PCM internal Low Side Driver (LSD) is functioning properly.

COMPONENT RATIONALITY DIAGNOSTIC OVERVIEW: A circuit fault against a component, or a sensor being used to monitor the system should be diagnosed before a rationality fault. Component and system rationality diagnostics are typically designed to detect a mechanical failure in a solenoid, motor, actuator or an overall system performance issue. However, do not assume that the wiring or circuits to the component are always good if you do not have a circuit fault. For example, a few Ohms of resistance in the power supply, control or ground circuit in a harness connector to a component could cause the component not to energize when commanded on and set a rationality or performance fault instead of a circuit fault. Rationality faults are often designed as a catch all for any failure that could be missed in other diagnostics. It is always a good practice to learn and understand how the rationality diagnostics are performed and the faults are detected by the ECU. Then check the connectors and circuits for any wiring issues (opens, resistance or shorted circuits) that could have caused the rationality failure, like a stuck on or stuck off solenoid, before replacing any components.