Up for sale is a Working, in excellent condition Mercedes PML Control Unit.   

MERCEDES E-CLASS 96 210 Type, ABS; (RH Rr eng comp), ASR (skid cont), (E320)
MERCEDES E-CLASS 97 210 Type, ABS; (RH Rr eng comp), ASR (skid cont), E420

.  This control unit performs a variety of functions in these cars.  A defective one can cause a whole host of potential problems, related to steering, ABS, throttle control system, malfunction lights, etc.

 Your best bet is to check the part number of the ECU you are trying to replace with this items part number to make sure they are the same. These units now have to be special ordered from most dealers new for big $$ (often times several thousand bucks!), and finding a good one second hand is getting to be a very hard chore.