W205 C250d temp sensor + catalytic converter inefficient following new NOx

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davg

New Member
Joined
Aug 13, 2020
Messages
14
Location
UK, Surrey
Car
2015 c250d, BMW M2
Morning all,

My wife’s 2015 C250d recently needed a NOx sensor. Really annoying and expensive issue given that the car is only just over 5 years old!

It has subsequently thrown a check ending light that came up as a temperature sensor and inefficient catalytic converters. Just wanted to see if this is an issue that anyone else has had or may be aware of. Managed to reset them and so far, so good. Would be good to know if expecting another big bill or if there is anything remedial we can do!

Many thanks,

davg
 
Update:

Engine light has not come back on, but the car went massively down on power after a motorway run today.

Any ideas? Is there a way to see how full the adblue is? Wondering if it could be something to do with this and it’s not come up with the warning saying it’s low!? At least hopeful that it is.
 
Really struggling to know what is best to do here! Feel like I should have taken it to main dealer for NOx initially to see if they would contribute. Now not sure whether to crack on with independent garage or take it to Merc.

Guess I can get the independent place to diagnose and go from there?
 
Really struggling to know what is best to do here! Feel like I should have taken it to main dealer for NOx initially to see if they would contribute. Now not sure whether to crack on with independent garage or take it to Merc.

Guess I can get the independent place to diagnose and go from there?

With the revised nox sensor mercedes need to do a software update, maybe the independant didn't do that?
 
Update:

Independent had done software updates etc. Exhaust Temperature sensor had gone. Had that repaired.

Subsequently the adblue warning came on and started countdown. Have topped it up but thecheck engine light and adblue countdown remains. also interesting to note that the last service in February, and less than 2000 miles ago, stated that the adblue was topped up and we were charged a lot!

dvg
 
Well the adblue systems can be a real pain,there is a lot of things that can go wrong,does the car only do short runs,you can get the adblue turn into crystals and block the pipe,it can be the temp sensor I see you have that fault coming up on the dash,I suppose that makes it the first thing to check,you have had a nox csensor changed which one there are two,as I say thats the problem with adblue eveerything has to work for the adblue to be sent to the valve to inject it into the exhaust,and thats the message you get adblue but it could be that temp sensor,you need to get it on star,to trace the fault,buying say the temp sensor could be a waste of money.
 
Really struggling to know what is best to do here! Feel like I should have taken it to main dealer for NOx initially to see if they would contribute. Now not sure whether to crack on with independent garage or take it to Merc.

Guess I can get the independent place to diagnose and go from there?
Hi I would have taken to a main dealer as these nox sensors are genially covered under the mb goodwill as a known issue.
 
Hi I would have taken to a main dealer as these nox sensors are genially covered under the mb goodwill as a known issue.

Unfortunately didn’t get that advice off the forum prior and the independent said that the dealer wouldn’t touch it. Wasn’t aware of them being covered by warranty at the time. Well aware now (NOx sensor, temp sensor and £1000 later!).

Mercedes assist have just been out. Looks like the independent had done the software update but hadn’t carried out the correct procedure to reset values for new sensors or something? Should be sorted now........
 

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