PCM Powertrain Control Module The PCM monitors the input and output signals produced by various sensors in the system, the PCM then adjusts the system as necessary. Sensors include: oxygen, coolant temperature, mass air flow, air intake temperature, crankshaft angle, throttle position, camshaft angle and engine knock. While computing feedback information the PCM adjusts and controls ignition timing, camshaft position, fuel injector input, fuel pump, cooling fan, emission system controls, forced air induction controls, traction controls and transmission gear selections. The computer operating program consists of a series of predetermined information cells, these cells hold the equation for proper vehicle operation. If the computer detects that it can't control a particular system it will illuminate the MIL (malfunction inductor lamp), aka check engine or service engine soon light. This means the computer has stored a trouble code. Visit - Scan for codes Trouble code definitions 1996 to present. Visit - OBD2 trouble codes
Helpful Information Communication standards were established in the OBD2 operating system development. These communication standards used a CAN (controller area network) system which can achieve communication speeds of more than 500 Kbps. Advantages of using information buses for communication is that if a fault occurs with any of the process modules, it can be reported separately to a diagnostic tool. Wiring is simplified by a technique known as multiplexing, a kind of wiring system which is assigned for each module. Sensor circuits operate on a 5 volt reference which drive system monitoring and control.