HELP C350 Decat exhaust

Alex Gray

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Hi all,

I was wondering if someone could assist on the new EML light I am having after fitting a decat to my Mercedes C350 Petrol 2012.

I have purchased M18 lambda sensor spacers but I can only find size m18 and it's too small for the secondary cat sensor's.

Has anyone had any experience with Decat on a C350 before? I have asked Mercedes Remap specialist and they suggested lambda spacers as they said it would be the easiest solution.

I would really appreciate the help.

Thanks in advance
 

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Craiglxviii

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Which Merc remap specialist did you ask?
 

LostKiwi

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With lambda spacers ;)
Won't help the emissions.
The emissions will be a fail with no cat.

The easiest way around a decat EML is using STAR but as decatting is illegal I'm saying nothing more!
 
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Alex Gray

Alex Gray

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The C350 comes with 4 cats so I have only removed the 2 larger ones further back. I have 1 sports backbox and 2 cats still. I also work in a garage that can do my MOT . I have tried lamda spacers but they don’t fit annoying they are too small, would anyone know of any other ways to fix my problem. Picture of the sensors I need to fix (pre opp)
 

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LostKiwi

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If you're only removing secondary cats the EML shouldn't come on?
 

Craiglxviii

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If you're only removing secondary cats the EML shouldn't come on?
That’s right, the secondaries are after the feedback loop sensors in the emissions control system.
 

L John

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I also work in a garage that can do my MOT
The picture in your first post shows your number plate.
My advice is be careful what you say on public forums.
I'm sure the garage you work at will do the MOT just the same as it would be done anywhere else.
 
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Alex Gray

Alex Gray

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The picture in your first post shows your number plate.
My advice is be careful what you say on public forums.
I'm sure the garage you work at will do the MOT just the same as it would be done anywhere else.
Thanks for the advise. I’ve already checked it doesn’t fail on emmisons there still okay because of the other cats. As for Eml light being on I can switch it of and it stays of for a while so it shouldn’t fail on that either so fingers crossed it will pass it’s next mot unless there’s something I’ve missed. On the other hand does anyone know of a way I can get this switched off permanently. Thanks
 

LostKiwi

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Sounds like you're suffering the usual V6 issue of a cracked front cat hence you're getting an error about TWC being below efficiency.
Just replace the offending front cat. Cheaper than pretty much anything else.
 
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If you want to totally disable the check engine light. I've copied the procedure I found on the SLK forums below.

Please note you will need somebody with access to Star Developer diagnostics.

""If you guys want to deactivate the check engine light. (due modifications for of road use LOL).

Go to:

Control Units->Information and Communication->IC-Instrument Cluster->

Diagnosis to plant specifications->Control Unit Adaptations->

Control Unit Adaptations (Variant Coding)->Variantenkodierung Werkseinstellungen (not menu)

Scroll to Check-Engine-Lamp (change from aktive to Passive).""

Then just reset the instrument cluster (again in Star) to activate the changes.

Regards

Gary

Sent from my SM-G930F using Tapatalk
 

LostKiwi

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If you want to totally disable the check engine light. I've copied the procedure I found on the SLK forums below.

Please note you will need somebody with access to Star Developer diagnostics.

""If you guys want to deactivate the check engine light. (due modifications for of road use LOL).

Go to:

Control Units->Information and Communication->IC-Instrument Cluster->

Diagnosis to plant specifications->Control Unit Adaptations->

Control Unit Adaptations (Variant Coding)->Variantenkodierung Werkseinstellungen (not menu)

Scroll to Check-Engine-Lamp (change from aktive to Passive).""

Then just reset the instrument cluster (again in Star) to activate the changes.

Regards

Gary

Sent from my SM-G930F using Tapatalk
That's using a hammer. That effectively disables the EML so preventing any malfunction from flagging.
It may also not pass an MOT if the light never turns on in the first place.

As above, the EML is on because the ECU thinks the remaining cat is bad. Simply replace the cat and you're legal and good to go. You could also try swapping sensors side to side in case it's an issue with a failing sensor.

Many on here have V8s with the secondary cat removed (including me - the car came that way) and no issues at all. On my last MOT (last month) it was well inside the limits and has never had an EML on. If yours is lit it's because there's something wrong.
 

John Laidlaw

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Indeed, and what happens if you’ve another fault and no notification, thereby causing more damage? That’s a NO in my book. As LK replace the offending CAT
 


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