Diagnosis on my 606: bad CCU. Agree? - PeachParts Mercedes-Benz Forum

muleears · #1 03-20-2009, 04:12 PM

EDIT: I meant to say ECU

My 98 E300 had been running bad for some time and throwing a MAF DTC constantly, even when new ones were installed. The car ran better with the MAF unplugged, just no boost. With it plugged in it ran extremely rich, had no power and would sometime misfire. In this condition it was not really drivable.

My indy is now telling me the ECU is toast and the cause of all my problems. He has hooked it up to Isis, oasis, osmosis or some similar name of software that tells him the ECU is telling the wastegate to open and close at the same time. It is deciding to stay open and dumping all my boost, hence poor performance. Does this sound reasonable? Could this cause a MAF DTC? BTW the EGR has been replaced with a rebuilt and functions properly now.

What do you Doctors think?

nhdoc · #2 03-20-2009, 06:21 PM

The only thing I would carefully inspect all of the wiring before replacing an expensive item like the ECU (I assume you mean ECU - the main computer which runs the car). There are people who will tell you of rodent damage causing havoc with their cars and I'd hate to see you spend $2000 on a part only to have it not be the problem.

I wonder if a company like Speedtuning can test the ECU out of the car and see if it is behaving correctly? Perhaps drop them an email and ask? That costs nothing and it would help isolate the problem to the ECU from the rest of the car. They might even be able to reflash it and repair it rather than have to replace it.

TMAllison · #3 03-20-2009, 06:53 PM

The CCU doesn't make sense but the ECU as Marty points out could.

If the ECU is bad there ought to be some simple electrical tests that can be done to confirm that.......

The wastegate is controlled by the vacuum transducer below the air filter. On ECU wiring harness pins 18 and 37 you should measure between .08-1.2amps if the transducer is working properly. Pins 37 and 53 should read greater than 6 volts at idle and less than 4 volts between 1500-3000rpm.

muleears · #4 03-20-2009, 07:11 PM

I probably have my terminology wrong. My ___________ that they think is the problem can be re-programmed (re-flashed?) for less than $400. My cars data has already been copied and sent to these people who will program the ____________ and send it to me next week.

I have been told the wiring checks have been done.

Could this have caused the constant MAF DTC?

TMAllison · #5 03-20-2009, 09:34 PM

Your__________, sounds as if it is the ECU to me.

Its the computer that controls air/fuel along with many other things. They can go bad but is not at all common. Usually you order a new one for a couple of thousand coded to your VIN and then do some SDS work when it is installed to make it recognize everything.

Did it get sent out to a tuning company to reflash it?

muleears · #6 03-21-2009, 04:43 AM

I'm not sure what company it was sent to. I know they needed the VIN. We found out that the car used the '99 software. I guess because of the late '98 build date.

JimmyL · #7 03-21-2009, 11:02 AM

Again I am reminded why I targeted the '95 W124 E300 as the newest car I would consider. I can't imagine fighting these types of issues, which seem all too common.
That is why I fear the wife's FX35. Lord help us if the electronics in that thing ever fail.......

nhdoc · #8 03-21-2009, 11:11 AM

Well, it sounds like they have the situation in hand. I'm far from an electronics expert but would assume that a problem in the firmware could cause an issue and it could be "rewritten" to correct it. If they can reflash it for under $400 and guarantee it will solve the problem then it seems like a reasonable solution...still I'd have spent that money on having the performance upgraded and kill that pesky EGR system if I were sending out the ECU for reflashing anyway

As for Jimmy's comments...the only thing I can say is the electronics on these cars seems to be every bit as robust as the mechanics...but they are now 10+ years old and are bound to have problems. $400 is not much to fix it if that fixes it. You can hardly get a new pair of shocks installed for that. I think I have only read of one other ECU failure on this board, that's a pretty good batting average.

muleears · #9 04-02-2009, 10:47 AM

Indy just called and said the car runs better than he has ever seen it run. $400 to reprogram my ECU, plus a rebuilt EGR, plus a MAF (or two). I'll be tickled ----less if it runs right. Wish me luck.

KarTek · #10 04-02-2009, 11:23 AM

That is great news! I've been really sick for you having to deal with all the horse-ing around trying to find out the root of the problem...

muleears · #11 04-02-2009, 11:37 AM

Yeah, all it took was three months, several hundred dollars and a lot of agravation. Ironicaly, now I want to sell the car. I have my eye on an S class with the rebuilt and records...