W210 Check engine light
 

I have a '98 E320 Wagon with about 86,000 miles. The check engine light came on last month, so I took it to my mechanic and the trouble code was P0422 (catalytic converter). He reset the code and all was well for about a week and the light came on again. The same code came up, he reset it again and it lasted a few days this time. After a few days of the light being on, it went out by itself. About a week later, the light came on again.

Given the high price (PartsShop MUCH less expensive than dealer) of a replacement converter I would like to make sure it is really the problem before I replace it. If I really do need to replace it, the mechanic has two conflicting code documents: one says driver's side converter, the other says cylinder bank one, which could be the passenger side.

Any suggestions or help would be appreciated!

PO422 is for the left side cat.

Thanks. The light is now off again. Any possibility this could be something other than the converter?

Back again!
 

The CEL light went out for quite a while. It reappeared a few months ago...I bought a code reader....It had two codes....P0170 and P0173. From other posts on the forum, I figured it was the mass air sensor. I ordered the mass air sensor from MercedesShop last week and installed it yesterday. No problem until just now. The CEL came back on and it now is showing #1P0422, #2P0170 and #3P0173.....Help!

What are your adaptation numbers?

Steve:

I have done a search on adaptation numbers on the forum and read all of the related posts...I THINK I understand......!

My code reader is an Innova Equus 3100....I don't believe this reader is capable of giving me the adaptation numbers......Is it now time to take it to the mechanic?

Thanks!

Replaced Cat, CEL back on
 

I had the driver's side catalytic converter replaced yesterday and CEL reset.....CEL came back on today with code P0422....any suggestions?

Factory cat or aftermarket?

Aftermarket....

We have tried a few suppliers of aftermarket cats, and
will do so no longer on OBD-2 cars.

The code is actually a "catalytic convertor efficiency" discrepency.

This parameter is set by the factory, and cannot be altered.
We have seen a large number of 210 cars with failed cats, some 202's.
BMW 740's seem prone, as well. Very often the substrate in the cat breaks up, and rattles annoyingly at idle.

The aftermarket cats we tried were replaced with factory units, and the
problem was cured. Lesson learned.

Pre-96 cars we have used the aftermarket cats with success.
(1 O2 sensor per bank, vs. 2 per bank in OBD-2 cars).
Less stringent monitoring.
These are not the generic, cut-the-pipe-and-weld-it-in type cats.
We use those only on 80's Euro stuff where there is no real option.

We have emissions testing, and the annual state inspection can not be performed on a car with check engine light on, or readiness tests not having been met.

Thanks, I guess I will live with it...

What about the possibilty that the problem is actually one or both of the rear O2 sensors (post-cat diagnostic probe)?
Gilly

Since the car had been checked by a tech, I presumed the sensor voltages had been checked. Note to self, "stop leaping to conclusions".

In our experience, the cat convertor efficiency codes mean convertor failure virtually every time, but o2 sensor voltages should be checked first, of course.

Just a thought anyways, I know there are codes which will fault the rear O2 sensors, but I don't recall any that will tell you "slow response time", etc like the front ones, as the rear ones fluctuate very, very little since they are behind the cat. So, leads me to wonder, will the diagnostic chain lead to a code for a bad cat, when in fact it's a "dirty", ie contaminated or "lazy" rear O2 sensor? I mean "I don't know", but worth considering. I would imagine somewhere it must be mentioned in the MB diagnostic system for that code, such as in the diagnostic manual, I don't have access to those anymore, so can't check, but I remember you'd look up the code and almost always it'd list at least 3 or 4 different possiblities for a code and where to go to check out each possibility.

Gilly

PS and since I'm on a roll, I'd like to mention that diagnosing problems like this is never just a matter of reading a code and replacing a part. It's NOT that easy, the codes can be caused by a bunch of different things. Very seldom will will you read a code, check out what the code means, and the manufacturer will simply tell you to replace a part. There can be several different faults that can set the same trouble code, it's up to the mechanic to determine what the real problem is. Anyone who doesn't realize this is not a mechanic but simply a "parts replacer". This is NOT aimed at anyone reading this, just to clarify that......just stating the obvious.

Agreed, how many EGR valves do you think have been sold for 104,112 and 113 motors because the big,box store checked codes for free,
and the "computer" said EGR malfunction--
See that code 4-5 times a week,
sell maybe 1 valve a year.

Just to clarify, the car was diagnosed where I used to live two years ago by a competent Mercedes mechanic. The catalytic converter was rattling (the noise is now gone) since I bought the car (with 75,000 miles on it). The CEL would come and go over the last two years, but has stayed on constantly for the past 3 months, so I thought it was time to fix the previously diagnosed problem. The local Mercedes dealer installed the cat the other day and offered no other explanations (they were short staffed for the holidays), except to tell me that P0422 was NOT the converter and installing the new converter would not clear the CEL.

I do not enjoy spending money to just "part replace," especially with the cost of Mercedes parts and most especially if replacement is not needed. It is difficult to find a competent Mercedes mechanic where I live. The shop I had found was severely damaged by hurricane Ivan and was not open. While I appreciate suggestions and comments, I thought this forum was for Mercedes owners to find help, not get lectured. I don't believe I have ever claimed to be a mechanic. I have enjoyed fixing minor issues and doing scheduled maintenance over the years on all of my cars. Again, I appreciate suggestions, but I can say that I have never been lectured on any of the Acura and BMW forums I have followed and posted on over the years.

SEE, I even "warned" you to NOT take this the wrong way! I wasn't aiming this comment at anyone in particular, just a warning that a code can be interpreted the wrong way if you're not careful.

Gilly

jford,
If I have offended, or lectured to you, I apologize.
Not my intent, whatsoever.
I don't think Gilly was trying to lecture you, either.
He specifically stated this in his comment above.

I, like you, am not a Mercedes mechanic.
I do, however, work with a few of the best in the business,IMHO,
and procure for them the parts needed for them to do their job.
I have done this for the last 15 years, and like to think I have learned a thing or two along the way. I also handle a large portion of the customer write-up and service advisor duties in our shop.

If the cat was rattling, then it was no good. Period.
However, there may very well be an additonal fault.
I am surprised a M-B dealer would install an aftermarket cat.
I know no local dealer would, but that may be due to emissions testing.
We have had problems with the aftermarket cats.
I will not cite engine management or OBD-II theory here, as I am not
capable. I will leave that to Steve B. and others more qualified.

I have no problem with you handling minor issues and maintenance on your own, and, in addition, whatever level of mechanical work with which you are comfortable.
I think it's great, and what this forum is about.

You asked for help, and I tried to help.
Gilly offered a possible item to be checked further.
I am curious as to what response you may have found more helpful?

Tx Benz: Your response has been the most helpful to my situation. I appreciate your insights. I was referring to Gilly....warning or not, Gilly was lecturing. Giving someone a warning not to be offended about something means you know you are about to offend someone, but you do it anyway.

Well,
I read this a dozen times and all I see from Gilly is an " Et Al" Post Script
to your thread .
And it's content is a simple information message making the readers aware of the mis-interpretation of codes and their association with incorrect part changes .
Quite common, and one should thank him for pointing this out.....

Mmmm, not always. I just knew that it would be possible for "someone" to jump to the conclusion that they were being accused of being a parts replacer at best and at worst have really strange ideas about the proper maintenance and repair of automobiles in general and Mercedes-Benz in particular, are a little too fast to judge, are confrontational and unappreciative and smell "funny". Oh wait, I did warn you to not take this thread the wrong way either, didn't I? Dork.

Gilly

Well, gee Gilly, I guess I should blame the original mechanic for the diagnosis and RPM55 for confirming the meaning of the code (not to mention the cat rattling, indicating that it needed to be replaced.) It never ceases to amaze me that some people feel the need to be so condescending on a forum where people are looking for a little assistance.

As long as you have someone to blame, it's OK.

Gilly

Gilly

Even if you don't play hockey, I think you should get one of those plastic " cups " to wear.
Seems to me some people really enjoy kicking you in the balls. :rolleyes:

Yeah no shixt, glad you noticed.

Gilly