200q ABS inoperative

[Eyvind Spangen]

The ABS in my '90 200q doesn't work.
Problem: Completely dead. No light in the dash, no ABS either.
All units test OK. Tried replacing the "brain" with a known-good unit, it made 
no difference. For some reason, the longitudinal acceleration unit under the 
rear seat is missing, but this shouldn't disable the whole system? Power 
supply/ground is OK.

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Regards,
ES