MOTRONIC CEC System: Description
In addition to a standard volt/ohm meter, jumper wires and connectors, some special testing equipment and BMW-specific procedures are REQUIRED for proper diagnosis of the Motronic system. The "BMW Service Test Kit", Bosch L-Jetronic Fuel Injection Testing Procedures Brochure, and BMW Test Meter (12 6 400 , 13 1 092 , 13 1 094 and 22 13 100 ) are REQUIRED to properly test Motronic systems. This equipment will be referred to throughout the following test procedures and MUST be used as indicated. Failure to do so may result in unnecessary replacement of good component parts. The information in this article will guide you, but without the BMW-specific tools, only basic tests can be performed.
The Motronic Emission Control System is an electronically controlled, computerized engine system which controls fuel injection and ignition timing as well as air/fuel ratio.
The Motronic Control Unit (MCU) is the "brain" of the system. Various engine sensors supply the MCU with operating information including air flow, air temperature, throttle position, coolant temperature, engine speed, piston position and oxygen content of exhaust gases.
The MCU uses this information to determine engine operating conditions, and adjusts timing and fuel ratio accordingly. The MCU is located behind the speaker in the right kick panel of 633CSi and 733i models and in the glove compartment of the 528e and 533i.