PCM EPROM

The PCM has an Erasable Programmable Read Only Memory (EPROM) computer chip that contains the calibration information used by the PCM to control fueling, idle speed, ignition timing, transaxle shifts and vehicle emissions. The calibration information is based on various aspects of the vehicle, such as engine size, vehicle weight, transaxle type, final drive ratio, etc. The EPROM is programmed (flashed) with the calibration information that is critical to proper operation of the PCM. The EPROM is soldered into the PCM and cannot be serviced separately. Replacement PCMs used for service come with all the necessary programming already installed.