NOX nightmare

[Spd2024]

Hiya,

Another dreaded nox sensor post. I’ve went through tons of threads, but I can’t find the answer to my question.

The EML light came on our 68 GLC 3 days after we drove it away, luckily it’s under warranty from the garage we purchased it from. They changed one and a few days after the EML came back on, it seems they didn’t realise they need to be coded in.

Last month the adblue needed topping up, after I did that the dreaded Adblue message came up saying I have 500 miles until engine won’t start, luckily the sensors came in shortly after that, they’ve fitted two new sensors and it goes into the dealership next week to be coded in. However the adblue countdown is still showing….. will this go after the sensors have been coded in? I’ve asked if they can do a new diagnostic to see if there is any adblue faults but none are showing.

Such a shame as I love the car, but the stress of a adblue car is ridiculous!

Thanks for your replies

 

[Spd2024]

Sorry to follow on this the above, I’ve just been told there is now a code, an issue with ad blue that links to the pre cat NOX Sensor. Does anyone know if that will be fixed when they code the sensors in?

Thanks!

 

[DSM10000]

Cars with Adblue and Nox sensors are going to be an ingoing money pit after the warranty has expired.

Mercedes have had issues with the Adblue tank sensors failing. I believe this is a £1500 fix.

I would be rejecting the car and looking for something else without Adblue.

 

[rayaans]

Or just put an MB warranty on it and call it a day and then sell it before it gets to 10 years old.

 

[Spd2024]

We have warranty with Cazoo who we got the car from, and they’re fronting the bill. Annoyingly I didn’t know our warranty allows us to go to the dealership otherwise I would have taken it there in the first place rather than cazoo who fitted the first sensor and didn’t code it in.
I just want to know the likelihood of getting our car back without the adblue countdown next week after the dealership have coded both sensors in (the courtesy car we’ve been given is half the size which is not ideal with two iso fixes and a double buggy in the back ).
They’ve also said the car was called for a software recall last year, which I’m wary of as I’ve seen endless threads about that messing up sensors etc!

 

[DSM10000]

We have warranty with Cazoo who we got the car from, and they’re fronting the bill. Annoyingly I didn’t know our warranty allows us to go to the dealership otherwise I would have taken it there in the first place rather than cazoo who fitted the first sensor and didn’t code it in.
I just want to know the likelihood of getting our car back without the adblue countdown next week after the dealership have coded both sensors in (the courtesy car we’ve been given is half the size which is not ideal with two iso fixes and a double buggy in the back ).
They’ve also said the car was called for a software recall last year, which I’m wary of as I’ve seen endless threads about that messing up sensors etc!

I don't believe that the Nox sensors and the Adblue countdown are related. Why not ask the dealer that is recoding the sensors? I I doubt that they will investigate the Adblue issue without authorisation from the warranty company.

The warranty you have at present will expire and taking out extended warranties for several years will be expensive.

 

[Spd2024]

I will call the dealer again and make them aware, just incase Cazoo haven’t. I spoke to Cazoo again and they seem certain the adblue will be fixed as the code is linking the adblue to the cat NOX sensor, but I know they’re not a Mercedes specialist so I think they’re hoping that’s the case.

If in worst case it needs a new adblue tank/pump, does anybody know how long it’s taking for those parts to come in? Are they on back order like the sensors….

I’d happily not see the word adblue and NOX for the rest of my life after this

 

[markjay]

Or just put an MB warranty on it and call it a day and then sell it before it gets to 10 years old.

It's not that simple... MB cars with EU6 Diesel engines have been known to be off the road for days or weeks due to difficult-to-diagnose AdBlue issues. A warranty will deal with the financial side of things but not with the inconvenience.

 

[rayaans]

It's not that simple... MB cars with EU6 Diesel engines have been known to be off the road for days or weeks due to difficult-to-diagnose AdBlue issues. A warranty will deal with the financial side of things but not with the inconvenience.

Thats a good point actually for the diesels

I suppose with the petrols you can just drive them around regardless of when the NOX sensor goes.

 

[TC350]

Thats a good point actually for the diesels

I suppose with the petrols you can just drive them around regardless of when the NOX sensor goes.

That’s certainly been my experience with NOx sensors flagged up as failed on my petrol car. I now suspect that just because the computer says that they’ve failed doesn’t necessarily mean that they have failed. The first couple of times the codes were flagged up to say that they had failed I got them replaced by MB, firstly under warranty and then as a “gesture of good will.”

When the EML came on again with the associated NOx failure code I was too busy to bother with chasing MB then getting them replaced, so I just cancelled the code on my cheap reader. It came on again after a week or two, so I cancelled again. This repeated for a couple of months then nothing. At least a year later it reared its ugly head again, so I went through the same process until it gave up alerting me.

The car has been serviced and MoT’d at my local MB dealership every year since I started this ritual, with no reports of anything untoward. I can’t help thinking that this is an issue of a ‘cracked hammer’ - like the story of train wheels being replaced many times before someone realised that the hammer used to bang the wheels, and listen to the sound as a method of checking for cracks, was itself cracked.

In the meantime, the manufacturer of NOx sensors has made a fortune from all the replacements thanks to a software glitch. Perhaps?

 

[Slartibartfast]

It's not that simple... MB cars with EU6 Diesel engines have been known to be off the road for days or weeks due to difficult-to-diagnose AdBlue issues. A warranty will deal with the financial side of things but not with the inconvenience.

There's also the "currently not available" saga which makes things worse. Sometimes 6 months or more "out of stock"!

 

[ALFAitalia]

I don't think that anyone who looks at this site on a regular basis would ever buy an AdBlue Mercedes!.....its certainly not a good advert for modern Merc diesels!!

 

[markjay]

Thats a good point actually for the diesels

I suppose with the petrols you can just drive them around regardless of when the NOX sensor goes.

An issue with one of the emission-control systems will cause the EML to light up, on both Diesel and petrol csrs, and if drivability is not affected then this will need to be rectified befire the next MOT.

An issue with the AdBlue system or one of its dependants, will also bring up the dreaded '500 miles' warning and will immobilise the car if ignored.

AdBlue problems are not fun....

 

[Smiley]

To be fair to MB it is not just MB cars that have this problem - it appears to be across all makes. And the price of the components seems to be in part driven by royalties payable to the inventor of the system. Maybe he was so very smart that he designed in flaws and unreliability........
Meanwhile the real answer is just don't buy the cars; it is not just the expense it is all of the hassle.

 

[Delderek]

There's also the "currently not available" saga which makes things worse. Sometimes 6 months or more "out of stock"!

13 Months in my case, and still not available. (C class petrol W205 2016)

 

[rayaans]

13 Months in my case, and still not available. (C class petrol W205 2016)

What isnt available?

Ive had my NOX sensor replaced by MB under warranty this year. Took 2-3 months to arrive so not exactly drastic but I guess for diesel owners this will be problematic.

 

[DITTRICH]

You have my deepest sympathies. Modern diesel and ad blue tech is not all its cracked up to be, I'm afraid. Unless you do loads of miles or someone else is footing the repair bill, petrol will make more sense, IMHO. Let us all know what happens.

 

[Delderek]

What isnt available?

Ive had my NOX sensor replaced by MB under warranty this year. Took 2-3 months to arrive so not exactly drastic but I guess for diesel owners this will be problematic.

The Nox sensor, seems the one fitted to my car is different to most others.

 

[rayaans]

The Nox sensor, seems the one fitted to my car is different to most others.

It won't be. I've also got a C200. I very much doubt they changed the nox sensor on a C200 between 2015 and 2016.

Mine turned up in 2-3 months and it's been fine since

 

[Harryv40]

Hi Everyone
i am not sure if this is a record, but my B Class, 71 reg with 13505 miles after 18 months has developed a NOX sensor fault!
Its only got 15 months warranty remaining, will MB cover the costs or is it down to me?