C280: rough idle, ABS+CE light, jerks hard ... ideas?

[RProsser]

Hi guys.

U.S. based 1997 C280. 105K miles. Well maintained.

It was running fine until last night. Then all of a sudden:

- both ABS and CE lights came ON
- when put into drive or reverse, the car leaps / jerks HARD
- now in limp home mode

All of these symptoms happened at the same time. What could this indicate?

Note: It goes in for maintenance (or I do the small stuff) on a regular basis. Four months ago, my German mechanic said the wiring harness still looks good.

Any input is appreciated!

- Rob

[Arthur Dalton]

Do a serch on "OVP"

http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=21H0MN3YU21N0PW5Q0&year=1996&make=MB&model=C-280-001&category=P&part=Overload+Relay

[RProsser]

Thanks. Will do.

I'll dig deeper, but upon doing a quick, cursory search of "OVP," I see reference to rough idle, but not both ABS and CE lights, nor any mention of the hard, abrupt leap when put into drive or reverse.

But obviously something electronic has gone on the fritz.

[Arthur Dalton]

...if you have a blown fuse on the OVP, you will ALWAYS get an ABS light.....
Thats why you want to search further.
That is what POWERS the ABS module..

[RProsser]

Okay, got it. Now since you are so adamant about the OVP, I assume you are saying its malfunction (ABS light coming on) could also be connected, in some roundabout way, to the simultaneous check engine light, the rough idling, and the transmission's very abrupt shifting.

I hope it's that easy.

I fear it's a control module $omewhere, so I hope you are right.

Thanks again.

[Arthur Dalton]

Not adamant about anything.
You asked for a possible solution and I direct you to the most common fault and FIRST suspect for your condition.
The reason I sent you to the archives was b/c of the enormous amount of OVP info stacked there ..It would be much easier for you to find this than for me to explain to yuo the whys of OVP problems
Just a tip..the OVP controls the ECU Engine Management power for your chassis and a faulty one will not only trigger an ABS warning, but it ill also cut power to both fuel and ignition on HFM/SFI systems, thereby triggering CE
Just a starting point. but one which I would check out first..
The OVP was eliminated on your chassis late in it's production, so make sure you have one for openers ..and if you do, check the fuse on top of it.
CE can be scanned for codes , but I would do that after checking into OVP first, as if that was the problem, the codes will clear themselves..if not, then go get it scanned ..
And when checking the archieves , you will notice there has been an updated , modified OVP part # for your chassis...so , if you have tyhe old part#, I would change it regardless...

[RProsser]

Thanks Arthur ... your added input brings the needed relevance.

I looked in the rear (pulled everything out) and the front (under the plastic covers) and cannot see anything that even closely resembles the OVP relay in the photo. I can only assume my car is a late model and it doesn't have one.

On further research of the threads (now I have more time), I find the symptoms indicate a rear differential sensor may be out. Easy replacement. Let's hope it works.

-Rob

[RProsser]

This evening I swapped-out the rear differential speed sensor ($95 from the dealer -- only 1 dealer had it in stock in all of my area.)

- Start the car.
- Put in drive. This time, there was no hard JERK.
- It shifted smoothly through all the gears.
- The ABS light went out as soon as it hit 2nd gear.
- The check engine light stayed on for about 10 miles.