I've done an exhaustive search on this code. My friend's E320 wagon has the CEL illuminated. I pulled up a code 17. It has something to do with one or more control modules not communicating with the other(s). The problem is I can't seem to find out what that exactly means, a new control unit somewhere? When the code is cleared, it returns after a few hours/days of driving. The car drives as beautifully as ever and fuel mileage is not effected. If anyone knows what that code means, that would help greatly - it seems to be very common on E420s I've read, not only code 17, but the fact that one module has stopped communicating with another.

The second VERY interesting piece to this puzzle (and I'm hoping this will bring forth an answer) is that while the CEL is illuminated with the engine running, it remains illuminated for about 45 seconds or so AFTER the engine is turned off and the key is in hand. Anyone ever heard of that with a CEL before???

Someone must have heard of this before. A. Dalton??? M.B. Doc???

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.

I've cured this the same way, but didn't have the glowing light after turning off. It also had some voltage implausible code.

I also helped a friend with his TE with a battery-drain issue, which turned out to be water in the OVP relay.

Troublesome buggers.

__________________

Gone to the dark side

- Jeff