CEL Light Exhaust C63 C204

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BigMatt91

New Member
Joined
May 27, 2020
Messages
8
Location
Scotland
Car
C63 W204
Hi

I bought a C63 in June (2014) the dealer said it had secondary cat delete and all was well

I took the car to a dealer who asked if i wanted gearbox and engine update i agreed

Now I think the car had been remapped because it feels slower now and the CEL light has come up, i can reset the code and after a couple of days it comes back on (PO420 and i think PO430)

Now im thinking that perhaps the primaries have been gutted , is this possible? Looks like the primaries are still in place

Car doesnt sound insanely loud
 
What are the descriptions for the 2 codes ? Do they come straight back or only after driving for a while
 
Im at work just now and just have a picture of the one code it says

(Catalyst System Efficiency Below Threshold Bank 1)

the other one is the same I think but for Bank 2

I can check later

I reset them and drive a few hours then it comes back, its not instant
 
Okay so if you have an efficiency fault then itsore than likely either the 2 downstream o2 sensors ( after the cat) are playing up or you have had both cats removed and so the o2 sensors is actually doing its job of telling the engine ecu that the cat is not working correctly. As you stated you think you may have had a map and when you had the engine and gearbox updated it has now over written the map which by the sounds of it factored in the cats being removed. The primary o2 sensors before the cat tell the ecu what the fueling is either lean or rich and the secoundry sensors check how well the cat is working. I would have a look inside the exhaust pipe ans see id the cats are there if not looks like you may have to see if you can get a map re loaded to factor this in
 
I'd say the dealer has overwritten a remap which has triggered the EML.
The fact you find the car slower suggests it was remapped, unknown to you.
Possibly the primary cats have been gutted and the O2 sensors were mapped out.
As above, putting the map back should turn off the EML and stop any more fault codes.

If MSL did the mapping they can check the cars history and assist with the map.
You should check the insurance implications if you do go ahead and remap.
 

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