Processor evidence
Bosch's Automotive Electrics and Automotive Electronics, page 199, figure 3, shows an M4.3 example with an 80C517. The Siemens SAB 80C517 manual describes that microcontroller as 8051-compatible. The chart is an example, not a processor specification for every M4.3 hardware number.
Application example
The Bosch vehicle component catalogue lists Volvo 850 turbo engines B 5234 FT, T and T4, September 1993 to August 1997, with M4.3. The dates and engine examples are catalogue scope, not a complete fitment list.
Identification and scope
Record the Bosch and vehicle-manufacturer ECU part numbers, engine code, market, year, hardware and software identity. Identify the processor from the specific unit before relying on its architecture. No pinout, interchangeability or programming procedure is established by a family designation alone.