Purpose Of The System
The M5.2.1 engine control system is manufactured by Bosch to BMW specifications. In addition to quality improvement modifications, emphasis was placed on enhancing functions for OBD II and Tier 1 compliance.
M5.2.1 control modules utilize the SKE (standard shell construction housing). The SKE utilizes a modular connector configuration. There are a total of 5 connectors providing a combined total of 134 pins.
The modular harness connectors are color coded by cylinder bank on the M73. When removing control modules from the E-Box, note the color of the plugs and mark each module to prevent incorrect replacement. This step is important to prevent EWS III (3.3) ISN incompatibility.
The correct Universal Adapter for the M5.2.1 application should be used (#90 88 6 121 300). This will ensure the pin connectors and the harness will not be damaged.