Engine Control Module (ECM)

ECU Input And Output Chart:

The ECU consists of an 8-bit microprocessor, random access memory (RAM), read only memory (ROM) and Input/output (I/0) interface. Based on the information from the input sensors, the ECU determines the optimum control for the operating conditions and drives the output actuators accordingly. The ECU actively controls the operation of the Fuel Injection system, the Ignition timing via the ignition igniter unit and has full control of the Idle Speed Control system. Additionally the ECU interrupts the operation of the Air Conditioning and EGR systems under some conditions and controls the power to the Fuel Pump. In addition to this, the engine control unit monitors the input/output signals of the engine control unit (some signals at all times and others under specific conditions).

In the event improper operation is detected, the ECU will store an error code or codes indicating which component or circuit has failed. The codes can then be extracted from the self-diagnosis output terminal. There are 8 diagnosis items including the Normal State. The diagnosis results can be read out with a voltmeter or multi-use tester. Since memorization of the trouble codes is backed up directly by the battery, the diagnosis results are held in memory even if the ignition key is turned off. Be sure to extract the codes before disconnecting the battery as the trouble codes will be erased when the battery terminal or the engine control unit connector is disconnected for more than 10 seconds.