I'm going out on limb here but i guess your car is a California version of E320 and this a diagnosis control unit with the part number A0155454332. Just shoot me if i'm wrong.

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600SEL '91
300E 4Matic '88
240D '83
280SE '77
350SE '73
The most complex systems can fail in the simplest way.
Contra verbosus noli contendere verbis, sermo datur cunctis, animi sapientia paucis.

i don't believe in the lord! He's never bought me a Mercedes Benz.