W205 250d cel after NOx replacement

[dvg]

Hi all,

Annoyingly started having problems with our C250d. Only 5 1/2 years old with 60k on it so a bit frustrating to start having these issues already.

CEL came on a couple of weeks ago. Took it to a Merc specialist, possibly an error?, who diagnosed NOx sensor. Had that replaced.

Subsequently it came on again and was down on power. Took it back to said specialist expecting it to be NOx sensor #2 and another £700! Fault codes were temperature sensor and inefficient catalytic converter.

They cleared codes and said see how I get on. It felt down on power yesterday and CEL has come back on. I am assuming that it’s the same codes. Annoying that the main dealers I’ve spoken to won’t have a quick look at it - have to book way in advance. My other car is off the road till Tuesday too!

Any suggestions as to what it could be? Am I ok to keep driving it (orange CEL) without further damage?

Any help greatly appreciated!


DVG

 

[star]

You may not want to hear this, but mercs sometimes change them under goodwill foc. Did your specialist update the software?

 

[dvg]

Yes, I subsequently gather. A bit annoyed as the specialist said that Mercedes definitely wouldn’t help out as out of warranty, despite it being emissions related. Bit miffed that they didn’t suggest trying Mercedes first, guess they have a vested interest.

I would hope that they updated software, being a Mercedes specialist.

Mercedes assistance are on their way now as we are quite far from home and still covered. Will see what they say. Seems a little coincidental that it’s had the NOx done just a week or so ago and now this issue.

dvg

 

[dvg]

Just had Mercedes assistance around.

Upstream exhaust temperature sensor is super noisy so looks like that needs replaced.

Wondering if the initial NOx sensor diagnosis could have been misdiagnosed as the symptoms seem exactly the same. Could a failed temp sensor throw up a NOx sensor code too?

thanks,

DVG

 

[star]

Noisey temp sensor??? That’s new to me. A temp sensor Fault will not Bring up a Nox fault and not all indies have invested in online star diagnosis equipment, so cannot update software.

 

[dvg]

Noisey temp sensor??? That’s new to me. A temp sensor Fault will not Bring up a Nox fault and not all indies have invested in online star diagnosis equipment, so cannot update software.

Thanks, star.

Sorry, probably used incorrect terminology. The temperature sensor is playing up basically and giving erratic readings from my understanding. Pleased that this wouldn’t cause a a subsequent NOx code as this means we haven’t wasted a load of money on a new one! Just wondered if the temp sensor failing could cause one to flag up, much like the temp sensor failing can cause an inefficient catalytic converter warning. I’m no mechanic though!

I will be double checking that the appropriate software update has been applied too!

 

[dvg]

Hello again,

I am about done with this car!

following issues have arisen:

1. NOx sensor - not cheap
2. Exhaust temp sensor.

Now the adblue warning came on, topped it up and it won’t reset. Have been through 4 driving ctycles.
Any advice!?
Many thanks,

 

[ajlsl600]

everytime i read this subject i shiver, it comes up at least 2,3 times a week and seems to be benz latest "little,not so little earner "
they just cant seem to make them properly ,i do wonder how benz fair with these issues in the states ,i hope they are forced to extend the warranty on dpf,adblue erg, nox sensors ect . and i have decided that i simply dont use my ml250 for any short,shopping trips,it seems the only way to mitigate the chances tho i sure ladbrooks would give shxxe odds for it!!

 

[bladecrazy]

I was told you need to change both at the same time, merc didnt help me with mine despite me asking, times have changed with these cars for sure , good luck with it mine is going up for sale in march.

 

[dvg]

It’s incredibly frustrating. To be honest, I am now at the point of getting rid of it and not buying a Mercedes again. We are planning on changing that car to electric next year, moving house first and need a charger etc. EQC would have been on the list as a potential - it’s being scrubbed off now.

Is there a way to force an adblue reset? It’s just that countdown and refil adblue that keeps coming up. I only put 5 litres in, should I put more in and see if that works?

 

[dvg]

It’s incredibly frustrating. To be honest, I am now at the point of getting rid of it and not buying a Mercedes again. We are planning on changing that car to electric next year, moving house first and need a charger etc. EQC would have been on the list as a potential - it’s being scrubbed off now.

Is there a way to force an adblue reset? It’s just that countdown and refil adblue that keeps coming up. I only put 5 litres in, should I put more in and see if that works?

On top of this, should the CEL be orange when adblue refill warning comes on!?

 

[mersum1es]

After replacing any emission stuff, few adaptation values should be reset. And depending on Nox sensor typre softwate update might be needed. It is not your mercedes fault but problem of misuderstanding how these systems should be repaired, or if not official procedure wanted, how to (illegal) tweak the system. SDS should do reset job. Online account ables to updates and couple of other programs direct tweaks.

 

[dvg]

After replacing any emission stuff, few adaptation values should be reset. And depending on Nox sensor typre softwate update might be needed. It is not your mercedes fault but problem of misuderstanding how these systems should be repaired, or if not official procedure wanted, how to (illegal) tweak the system. SDS should do reset job. Online account ables to updates and couple of other programs direct tweaks.

many thanks for the response - the independent specialist has all of the main dealer capacity to do with updates and did all of the software updates required.

I’ve called out Mercedes assist as the countdown means that we will break down before the next appointment t our local dealer. Interestingly, it says in the service record that the adblue was topped up at the last service in February (which I think we were charged for). The car has only done 2000 miles at most, which seems odd in itself. It took the top up that I put in.

 

[mersum1es]

Ok, everything just pointed there were shortcuts used...

Well then they have all equipments, hope they have will to finish the job too.

NoX sensor has been real PITA in these cars, thats why they have done plenty of them as goodwill. Though some dealers/indys have messed that too like said above, they have not done proper reset.