Subject: Automobile Engineering

Topic: Recent Trends in Automobiles

Difficulty: Medium

The Engine Control Module (also called power train control module or PCM) is the brains of the engine management system. It controls the fuel mixture, ignition timing, variable cam timing & emission control. It constantly monitors emissions performance via its OBD (onboard Diagnostics) programming & it oversees the operation of the fuel pump,engine cooling fan & charging system. It also interacts with the transmission controller (if separate), ABS/ traction/stability control system, body control module, climate control module & anti-theft system. In short, the engine control module performs a wide variety of functions that are necessary to operate a vehicle.

The electronic components inside an engine control modules are fairly robust, but sometimes things con & do go wrong. Shorts in sensors circuits may over load & damage the module. Problems with the module's power supply (too much voltage or not enough) or ground connections can cause it to misbehave. Rod inputs from sensors or other modules may also cause it to malfunction. Corrosion, excessive heat & vibration also can cause harm to the module.

When the engine control module fails, it may or may not set any Diagnostic Trouble Codes (DTCs). This can make troubleshooting difficult & often results in misdiagnosis of a bad computer. Often the real problem is outside the computer such as a bad sensor, wiring fault, power relay or voltage issue. Complete module failures are rare, but failures within the module's various subsystems & memory are more common. A shorted fuel injector, for example, may overload & burn out the injector driver circuit within the engine control module. If the underlying cause is not found & fixed it can cause the replacement computer to fail, too,