RE: this vague code 17 with an illuminated CEL. I've asked many people what this means and no one knows except that it's a "lack of communication between ECUs" - whatever the heLL THAT means. I figured out first of all that it was this nebulous code that didn't really have any meaning. My friend brought his car to an MB independent who read code 17 as meaning/automatically needing a new CPU for $2,000+. Secondly, I started following the MB factory manual troubleshooting page for this code. Step 1 said to check the 15 amp fuse in the OVP relay. Knowing that in all the 124s, the OVP is very fickle and flaky, I took it one step further and replaced the whole OVP with a used known working one. I then cleared the code, my friend has driven a total of about 2,000 miles since then and the the CEL has not re-illuminated. This troublesome OVP was an aftermarket (3 month old) brand made by "URO" (no doubt China since the country of origin wasn't marked anywhere on the box or relay). I replaced it again with a new MB-brand made by a company (forgot who) in Hungary. Problem solved.