Anybody have this happen? I can't say I'm surprised but as much as I read about removing the resonator, I can't remember any posts saying the check engine light came on as a result of the removal. Suggestions? Other experiences? I kept the resonator so I could put it back on easy enough but I was hoping to leave it off. My next move was going to be removing the secondary cats but I'm holding off until I figure out this issue first. For reference, I own a CLS55 AMG.

 

Removing the resonators shouldn't set of any codes. It could just be a coincidence that something else went wrong, but before we get into that, are you certain they removed the resonators and not the cats? Can you take a pic of what was removed?

If you have a scan tool, see what code(s) you have...

 

I thought about the coincidence factor and that may be the case. I have owned the car for a couple of years now and have never seen the cel come on before. I had the resonator removed today and on the way home from the shop, the check engine light came on. I can't think of any reason why a resonator removal would cause a code but it sure seems like that's the case. It was definitely the resonator removed as I asked to look at the car before they lowered the lift and I have the resonator in the trunk with (4) cats still installed. I will probably end up brining the car to my local Mercedes shop to check the code.

 

Must be a coincidence as the only thing I could think of happening during exhaust work is an O2 sensor going out but those are located just before and after each of the primary cats....interesting.

Are you getting any different odor from exhaust like phosphorus smell as that may be an issue with an O2 sensor

 

If you're smelling anything even remotely phosphorous emitting from the exhaust system, chances are the problem is not so much from the O2 sensors but rather more with the engine and catalytic converters.

The main causes of cat failure (or the reason why you're smelling such a smell) are due to lead, silicone or phosphorous contamination within the exhaust system (or cats to be exact).

Lead... Thankfully has been removed from most of today's consumer based fuels. It is and can still be found in some high-octane race fuels or additives, which you shouldn't use on an emission controlled vehicle.

Silicone... Usually finds its way into the exhaust system through a coolant leak within the combustion chamber or more familiarly a head gasket. Believe it or not, some oil and fuel additives also contain silicone. In small amounts it may not be as harmful, but when used improperly (like pouring in 2 or 3 times the recommended amount) is when it can cause irreversible damage. Silicone can also cause havoc and permanently damage O2 sensors.

Phosphorous... Comes from motor oil (even though newer oils are said to contain little to none of it, they still do), and under normal conditions shouldn't be a problem for a "healthy" cat to keep under control but an engine that is burning oil from lets say bad valve guides, seals, rings, or gaskets will naturally contaminant even a "healthy" cat. This contamination in essence clogs the cat(s) and when the cat & exhaust system warms up, it emits the phosphorous smell you're picking up.

An internally damaged or broken cat can also be a culprit, as it's prevent the gases from properly flowing through. Any pocket or blockage can cause contaminants to be clogged or trapped. Even a small clog, due to the increase in heat, can render a cat or even the whole emission system useless.

A bad O2 can cause irregular smells from the exhaust, but it's usually more a "raw gas" smell than anything phosphorous like.

If by any chance you do get some sort of O2 or emission related code, I would carefully examine the rest of the exhaust system which may help you determine if there's anything else wrong with your car.

Just some more food for thought...

 

also after welding in new pipes to your exhaust, you will smell the residues from the welding for a while...