Click to Print
. . . . . . .
Thursday, September 1,2011

PCM Powertrain Control Module

By Teresa Aquila  
The PCM monitors the input and output signals produced by various sensors in the system. The PCM then adjusts the system as necessary. Sensors can include: oxygen sensor, coolant sensor, mass air flow sensor, air intake sensor, crankshaft angle sensor, throttle position sensor, camshaft angle sensor and knock sensor. The PCM operating program consists of information cells. These cells hold the code for proper engine operation. If information is outside the cell parameters a MIL (malfunction inductor lamp) or “check engine light” Illuminates.

Once a “check engine” or a “service engine soon” light in your instrument cluster has illuminated the PCM has stored a diagnostic trouble code. This means the computer system on your vehicle has detected a problem with the various systems it controls. Your car or truck has many different sensors that monitor the various vehicle systems. If the trouble code light has been illuminated your vehicle enters into “limp mode” this means it is running on a predetermined program that causes poor mileage and increased emissions. An engine trouble code reader is an easy to use tool. All 1996 and newer vehicles utilize a “D” style plugin connector that connects to the code reader. On most vehicles the connector is located at the driver’s compartment. Once the code reader is plugged in you can retrieve trouble codes the engine computer has stored in its memory. These codes are the same codes the dealer and repair shops use to replace sensors and clear codes. The PCM outputs a 5 volt reference to most sensors to drive the monitoring circuits. The PCM also controls the radiator cooling fan, air pump, fuel pump, EVAP system and more depending on the vehicle. Communication standards have been established in the OBD2 operating system. Among the communication standards controller area networking or CAN has become very popular and can achieve communication speeds of more than 500 Kbps, which is faster than most communication standards. Advantages of using buses for communication is that if a fault occurs with any of the process modules, it can be reported separately to a diagnostic tool. Manufacturers have different trouble code faults although some are generic. Wiring is simplified by a technique known as multiplexing. This kind of wiring system is assigned for each module, which consolidates the output and input for that module. Supplied by 2CarPros.


  • Currently 3.5/5 Stars.
  • 1
  • 2
  • 3
  • 4
  • 5