Based on this info I'm guessing the PSE is pulling down the body CAN (CAN B). The relationship between modules on the CAN is described quite nicely in this MB training document: http://www.mercedestechstore.com/pdfs/507%20Systems%20I/507%20HO%20CAN%20B%20(ICC)%2010-28-02.pdf

Pay particular attention to pages 47 and 48 as they specifically apply to the 210 chassis.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician