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Theory of operation:
Major systems:
ECM Revisions:
- MMS 200:
The MMS200 series was the first Engine Control Module (ECM) series for the 12v V6 engine,
used in the Audi 100 through October 1992 production. It was adapted from the MPI Engine Management
System for the Coupe Quattro and 90 Quattro 20-Valve and included On Board Diagnostic I (OBD-I)
capabilities. The ECM itself is made by Bosch and contains an 8-bit microprocessor with 48kB system
memory.
Engine Control Modules:- 4A0 906 266 A
- 4A0 906 266 AA
- 4A0 906 266 AB
- MMS 300:
With this version, the MPI ECM was completely rewritten. This ECU was the first to incorporate
adaptive learning functions such as oxygen sensor control.
The MMS300 ECM was used from October 1992 to early 1993 production in
Audi 80/90 and 100 models. The ECM is made by Hitachi and contains a 16-bit microprocessor with
60kB system memory. The ECM has the same four connectors as the MMS200 series ECM, but
the terminal functions are different and the control module is not backwards compatible.
Engine Control Module:- 8A0 906 266 B
Engine Control Modules:- 8A0 906 266 E
- 8A0 906 266 H
- 8A0 906 266 J
- MMS 400:
With this version, On Board Diagnostic II (OBD-II) was introduced for the A6 with manual transmission
and front wheel drive. OBD-II included the addition of a second pair of heated oxygen sensors after
the catalytic converters and new OBD programming. To accomodate new features, an additional 32
input/output pins were added to the ECM.
Engine Control Module:- 8A0 906 266 D
Engine Control Module:- 8D0 906 266 A
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