NoX sensors

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Discussion

robemcdonald

Original Poster:

8,716 posts

195 months

Monday 20th June 2022
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I have a 2018 C250D Estate as my daily driver.

On a recent trip I had an add ad blue message show up, so I did.

around 200 miles later another error message. This time it’s: can’t detect Ad Blue level and the car won’t start in 500 miles (on a countdown).

Turns out it’s a common fault with one of two NoX sensors. Problem is these things are a little bi hard to come by. So soon I’m going to have a £20k paperweight on my drive as Mercedes don’t stock / manufacture enough spare parts.

Any idea on what else I can do?

NMNeil

5,860 posts

49 months

Monday 20th June 2022
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I may be off base but isn't the AdBlue the chemical they use to inject into the exhaust to lower emissions on diesels. Maybe it's just what it says, a level sensor, much like the sensor that tells you when your windscreen washer fluid, coolant or brake fluid is low?
Being a Mercedes I'm probably wrong, as they love to make things complicated biggrin

DamienCBR

2,035 posts

222 months

Monday 20th June 2022
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Very common problem. If you are on Facebook join Mercedes-Benz Owners Club UK, lots of people have the same problem. If you are getting it done at main dealer and they are having issues getting the sensor they can do something to extend the 500 miles from what i have read.

I never had a problem with my 2016 E220d, put some in when it told me, had that car for 70,000 miles. My new e220d has a level that you can see, when it got to 1/4 full i put 10L in. I did it with the engine running as recommend somewhere i read, not sure if it really matter.

robemcdonald

Original Poster:

8,716 posts

195 months

Monday 20th June 2022
quotequote all
It’s booked into a specialist tomorrow.

I’ll find out a definitive answer then.

I’d be interested to know if anyone has had the issue.

Deano_BMW

428 posts

185 months

Tuesday 21st June 2022
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its a hugely common problem at the moment, with parts on back order i believe unless you go for non oem nox sensors.

it seems (whilst a very touchy subject admittedly) a very common thing to have the system removed and mapped out. and not have to worry about the issue going forwards.

PDP76

2,569 posts

149 months

Tuesday 21st June 2022
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Mercs eat nox sensors for dinner. So far I’m so lucky with the 4 sets I had 3 yrs ago on my 350.
They are on massive back order and have been for a while.
An aftermarket part will turn the lights out for a while but not for long.
For an mot fk knows what’s supposed to happen with that. Fit st parts to pass or wait. !
The last set I had on were supposed to be the updated parts and still going strong 3 yrs later.
Is it a waiting game or not for the yellow light of death !

robemcdonald

Original Poster:

8,716 posts

195 months

Tuesday 21st June 2022
quotequote all
Car still in the garage. I will know more tomorrow.

I’m really surprised this insurance a bigger. The more I look the more common it seems.

Should have done my due diligence when buying the car I guess, but who could have predicted parts not actually being available?

W201_190e

12,738 posts

212 months

Monday 27th June 2022
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I work for a specialist and we’ve had customers waiting months for them. We don’t use aftermarket parts anyway, but even so there are no reliable alternative options. I can tell you that there are none available in the UK or from Germany at the moment.

robemcdonald

Original Poster:

8,716 posts

195 months

Monday 27th June 2022
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The Indy has reset everything and brimmed the adblu tank, but it’s a ticking bomb and at some point the count down will start again.

I have to say this is extremely poor.

I have decided to opt back into the company car scheme and get an electric car. I really can’t be bothered with this nonsense.

Monkeylegend

26,226 posts

230 months

Tuesday 28th June 2022
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It is not just the NoX sensors, the adblue pump which sits inside the tank is also a known problem requiring a new tank and there are also wiring loom issues related to the system as well. Replacing the sensors and the tank can be a £2/3k job if there is no goodwill from Mercedes.

Replacing the NoX sensors only buys you time until it happens again and as you say they are on a several months back order for genuine parts.

The NoX sensors are affected by water/condensation in the exhaust and Mercedes remedy is to drill a hole in the exhaust to allow the water to drain out.

It is a big issue for Mercedes and they are facing a class action in the USA.

Avoid the BlueTec cars like the plague. It also is a problem with their petrol engines as well.

Chicken Chaser

7,744 posts

223 months

Friday 6th January 2023
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Bit of a thread resurrection but I've had a nox sensor flag up on my Mercedes too. Same tale, parts are on back order and no date for supply. When it does arrive it'll be £750 to supply and fit. I'm stuck without but it appears there's little other option. Aftermarket sensors don't last, apparently a delete is a bad idea as the exhaust runs too hot and melts neighbouring parts. I'm equally concerned that the sensor is replaced then another part of the system malfunctions and costs more again.