As I understand it that control unit does 2 things:

Kick the transmission down to first from 2nd when you remove your foot from the brake pedal (the car rests in 2nd).
Limit boost in first gear to protect the transmission.

-J

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1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.