Powertrain Control Module (ECM)
A malfunction is detected by using a checksum technique for verifying data. The digital data is composed of zeros and ones. A checksum is the total of all ones in a string of data. By comparing the checksum value with a stored value, a malfunction can be detected. The ECM keeps internal counting to calculate the model values related to temperature under Ignition "OFF" condition. ECM uses this values to improve efficiency when the engine starts again. The ECM monitors errors through checksum. Every information consists of the combination of 0 and 1, checksum means summing up all values in a row. Thus, errors are recognized comparing checksum value and the memory value at the ECM.