1994 C280 -- New Wire Harness -- STILL won't start - PeachParts Mercedes-Benz Forum

Nate · #1 08-15-2006, 01:08 AM

still got it?

brookspw · #2 08-16-2006, 10:49 AM

Quote:

Originally Posted by Nate

still got it?

It looked pretty bad. Very "crispy" and brittle. A couple of the connections cracked upon removal. Saw many exposed wires. This car has only 60k miles.

Only took me about 3 hours to replace. 1 hour of that was figuring out the big hookup just behind the left headlight. It fed 4 different wire pin connectors to the new harness. 1 of those 4 wasn't in the new harness and getting that one was a pain.

Yes, I still have it.

Can anyone comment on my question regarding the O2 sensor?

Arthur Dalton · #3 08-16-2006, 10:56 AM

The rear 02 code should clear after you solve the problem and the cat heats up and burns off the mix. ..
Again, I would Change the OVP.,

brookspw · #4 08-16-2006, 11:07 AM

Quote:

Originally Posted by Arthur Dalton

The rear 02 code should clear after you solve the problem and the cat heats up and burns off the mix. ..
Again, I would Change the OVP.,

Phil has the OVP on the way. New part #, Siebel brand.

Explain your...explanation, above, please. Are you saying the rear O2 is not now working due to the OVP?

Arthur Dalton · #5 08-16-2006, 11:34 AM

Your cars Engine Management Sytem has not been working , either due to wire harness or OVP voltage supply interruptions..[ or both]...so, the cat gets soaked and the rear 02 sensors job is to monitors the cats output. It fails the test and pops the code.... when the engine management is to spec , the cat will burn off the remaining crap and return to a normal specs.

This can also be accomplished by a hard run , under load [ read hill] AFTER the cause/s have been rectified .. [ with the OVP being the FIRST suspect]

It is quite common to see many parts changed before the OVP gets even looked at. With their notorious fail rate, this has always amazed me .. Specially when the owners have used a Benz Dealer .. just too hard for me to comprehend how this can possibly happen........but if you do a search, one will see it happens consistantly. I would venture to say that the OVP has caused more guys $2K due to mis-diagnosis than any other simple $60 , plug-in part.
I am one of those old school techs who, when we percieve an electrical power feed malfuntion, start at the front of the feed line [ Battery supply voltage] and work foward. The next stop , of course, is the OVP.. Now , I guess we could start at the other end [ The ECU] and work backwards to the voltage supply, but I am just lazy and want to find the problem as soon as possible.........meaning I am not as concerned about racking up the bill as I am at solving the problem.
Any good tech dept not only knows of OVP problems, but also has a known good OVP in their toolbox for rapid check/verification.

brookspw · #6 09-05-2006, 02:13 PM

Ok, Arthur, you were exactly right. Two weeks and no starting problems whatsoever. It was the OVP that was causing the problem.

This leads me, though, to a few questions:

1. The check engine light still hasn't gone away as you thought it would. When checked before, they said it was the rear cat O2 sensor. Runs perfectly now.
2. Mercedes Dealer charged me for r/r the crank sensor when they couldn't figure out what was wrong. As I mentioned earlier, that didn't help one bit. Now that I figured out what was wrong, how would you suggest I approach the dealer? I mean, I don't expect them to give me a refund necessarily, but a labor credit toward a next visit might be reasonable. $500 for the part and labor.

Thanks, P

brookspw · #7 09-23-2006, 11:50 AM

Bump, anyone have any suggestions regarding my previous post?