Knock Sensor needs replacing exhaust - quoted £1200!!!! :(

[Deleted member 65149]

Hi! I realise this thread is quite old, but I just came up against this problem. I have an electric diesel hybrid (C-class saloon), year 2014, which I just got 2 months back (purchased second hand), and now I have the yellow light on the dashboard as well. When I took it in to get a diagnostic done, I was told that the Nox sensors and an air filter are gone and need replacing. (I was given the part numbers). I was quoted £1200+ for this job, which is kind of crazy.

I found it very interesting to hear that you called Mercedes and that they covered your costs.

I do have a 6 month warranty, but they will only cover upto £500 of each claim, so it would still cost £700+ for this job.

Of course, I probably wouldn't get that benefit, but I was wondering if I could buy the parts online, which would be a lot cheaper (if I quote the part numbers and ensure they are the correct ones) and then get it done from any other service centre.

Any recommendations would be welcome.

Also, in this current condition, how long can I drive the car? I'm only counting on a few days and miles at most - basic errands, shopping, etc.

Thank you so much!

If your car has always been serviced by Mercedes then it would be worth giving them a call. The worst they can say is no.

However, if there’s an air filter sensor activated it sounds very much that servicing hasn’t been carried out correctly because this is one of the routine replacement items. It’s something you can do easily yourself. You could probably get a cheapish version from Halfords or on eBay but I would recommend the genuine part from your nearest MB dealer. It’s never worth skimping on such things.

As for the NOx sensors, you have to be very careful buying them yourself. There are still lots of the original ones around for sale that will soon fail again. The genuine replacements are a later design, that’s hopefully more reliable. But even they need the software updating when they’re fitted to ensure they don’t give false results. A good MB Indy can do the job for you a bit cheaper than MB, but the parts are really expensive so you won’t save much. If they say they can do it a lot cheaper there’s a good chance they’re using the old style sensors. I’m afraid that your best option will be to get them replaced by MB with your warranty covering some of the cost.

You can carry on using the car without any problem for a short while. The sensors are just telling you that things have gone a little bit out of the normal range. You won’t do any damage to anything by driving a few hundred miles with the yellow warning light on. Just don’t leave it too long or your DPF could get damaged and that’s another big expense.

 

[SomT]

Thanks for the very quick response.

I appreciate that.

Based on what I read here, I called Mercedes. They were polite and said that I would need to take it into an authorised Merc service centre near me, who would then run a diagnostic test (another £144!) - and then perhaps (perhaps maybe - just maybe) - they might offer to cover a part of it.

Obviously, getting it done by an authorised service centre would be even more expensive and then on top, there is the additional cost of getting another diagnostic done.

You might be right: it might be best to bite the bullet and go with it.

I wonder if the independent company that I got the original diagnostic done from is using the new or the older design. I do have the part numbers:
A0009051512 (Nox sensor) - as recommended by the independent German service centre
A6510940100 (air filter)

Is there a way to determine if the sensors recommended above are the upgraded ones?

Also, is it necessary to replace both Nox sensors if only one is gone? I suppose this is just for precaution.

What do you think?

Thank you once again!

If your car has always been serviced by Mercedes then it would be worth giving them a call. The worst they can say is no.

However, if there’s an air filter sensor activated it sounds very much that servicing hasn’t been carried out correctly because this is one of the routine replacement items. It’s something you can do easily yourself. You could probably get a cheapish version from Halfords or on eBay but I would recommend the genuine part from your nearest MB dealer. It’s never worth skimping on such things.

As for the NOx sensors, you have to be very careful buying them yourself. There are still lots of the original ones around for sale that will soon fail again. The genuine replacements are a later design, that’s hopefully more reliable. But even they need the software updating when they’re fitted to ensure they don’t give false results. A good MB Indy can do the job for you a bit cheaper than MB, but the parts are really expensive so you won’t save much. If they say they can do it a lot cheaper there’s a good chance they’re using the old style sensors. I’m afraid that your best option will be to get them replaced by MB with your warranty covering some of the cost.

You can carry on using the car without any problem for a short while. The sensors are just telling you that things have gone a little bit out of the normal range. You won’t do any damage to anything by driving a few hundred miles with the yellow warning light on. Just don’t leave it too long or your DPF could get damaged and that’s another big expense.

 

[Deleted member 65149]

I went through the same hesitancy about getting an official MB test done when I already knew that the fault was being shown as NOx sensors. I decided to bite the bullet and I was glad I did because MB stumped up £1000 towards the repair. But my 2012 C350 has always been serviced by MB and I suspect that may have been a consideration in their decision.

FYI, the bill for replacing both NOx sensors at MB Peterborough three months ago was £1177.20 - £1000. (In addition to that I paid them £132 for the diagnostic test a month before.) The bill showed the NOx sensors being £364 + VAT each. The part numbers shown aren’t the same as you gave, but that could be because my car is petrol.

My recommendation would be to get a quote from your MB dealer for replacing the sensors and if, as I suspect, it’s not much different to your Indy then get them to do the diagnostic test (query the charge - it was only £132 for me in August.) Ask the dealer to put in a request for factory goodwill. This is just a quick application on their computer, which will almost certainly get rejected. Then call MB UK again to ask for a contribution for what is clearly a very common fault with the original sensors. Then cross your fingers and hope for a favourable response.

In the meantime, buy an air filter and replace it yourself. I don’t know about your particular engine, but I’ve never known it to be difficult. Just make sure you do it before your NOx sensors get replaced because the Engine Management Light will need to be reset.

Good luck.

 

[SomT]

Thanks again so much! This is what I thought too. You're right - it might be that Mercedes will acknowledge the point that this is a common problem and obviously, since then they have upgraded the part.

I'm going to go ahead and call the MB service centre and see what their quote will be and based on that, make a decision.

I really appreciate your help with this and quick responses.

I went through the same hesitancy about getting an official MB test done when I already knew that the fault was being shown as NOx sensors. I decided to bite the bullet and I was glad I did because MB stumped up £1000 towards the repair. But my 2012 C350 has always been serviced by MB and I suspect that may have been a consideration in their decision.

FYI, the bill for replacing both NOx sensors at MB Peterborough three months ago was £1177.20 - £1000. (In addition to that I paid them £132 for the diagnostic test a month before.) The bill showed the NOx sensors being £364 + VAT each. The part numbers shown aren’t the same as you gave, but that could be because my car is petrol.

My recommendation would be to get a quote from your MB dealer for replacing the sensors and if, as I suspect, it’s not much different to your Indy then get them to do the diagnostic test (query the charge - it was only £132 for me in August.) Ask the dealer to put in a request for factory goodwill. This is just a quick application on their computer, which will almost certainly get rejected. Then call MB UK again to ask for a contribution for what is clearly a very common fault with the original sensors. Then cross your fingers and hope for a favourable response.

In the meantime, buy an air filter and replace it yourself. I don’t know about your particular engine, but I’ve never known it to be difficult. Just make sure you do it before your NOx sensors get replaced because the Engine Management Light will need to be reset.

Good luck.

 

[Deleted member 6183]

In this sort of situation I would be slightly wary of using an independent, not all are as well placed to help as others, my experience with BMW:
I once owned a 3.0 petrol E60 with coil pack problems. I was using an indy who was replacing these coils frequently, in the end I had spent nearly £1k on the things. On one visit he made a big show to me of phoning the parts dept of the local dealer and asking for availability of these parts, the dealer conceded that the indy had bought up their entire stock.
Over 12 months later I called at the dealer and grumbled about their crappy coil packs, the dealer confirmed that I should have been invited to bring the car in for the new upgraded coil packs! The indy had bought up their entire stock of crap ones.

I had the recall done and all good, I also spoke to BMW UK who refunded the cost of the Indy supplied parts.

 

[grober]

I do wish that posters that come on the forum with what are essentially technical questions would post up their VIN [CHASSIS] Number at the same time. It makes answering their questions so much more accurate. Its easy -- its there on top of the passenger side of the dashboard and can easily be read through the windscreen and will start WDB OR WDD etc.
ps this should be made a sticky somewhere if it hasn't been already.

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[Craig Mikehow]

FWIW I had a NOx issue over Christmas. Started with the EML. NOx sensor was identified by my local independent, who cleared it for long enough to pass its 2nd MOT. They suggested when it happened again, go to the main dealer. It came back on about 3 days later. Took it to MB Watford last week for an ‘official’ diagnosis (£120) and it was confirmed by them as a faulty NOx sensor. I was not long outside of an extended warranty and discussed with them the weakness of the original sensor. MB Watford offered to speak to MB HQ about out of warranty swap and they refused due to car’s age (Jan 15) but the dealer as a gesture of goodwill agreed to pay half (I’m on a service plan with them). All in, cost me £348 including the diagnosis charge, fitting and new sensor rather than nearly £800 so I’ll take that as a win.

 

[DITTRICH]

I reallyfeelfor you poor people with modern diesel engines. My s124 E300 diesel was literally bullet proof but sadly not partner proof. The replacement is a petrol. My local MOT garage mechanics all drive cheap euro 4 ulez compliant petrol cars.

 

[E55BOF]

'Bangernomics' doesn't suit everyone. Your 124 may have had a bullet-proof engine, but driving an ancient design on modern roads also doesn't suit everyone.

 

[Deanw23]

Just sharing my experience, a month ago my fuel relay unit went then 3 weeks after that my ad blue injector was blocked, then last night my engine management light came on showing fault code po4020 catalytic converter, took it to Mercedes Maidstone today and was told both Nox centres need replacing at £430 plus vat each and 2 hours labour. The dealership said don’t worry we are going to make a phone call to MB head office, she came back 10 minutes later and informed me MB are going to pay 100% of the bill and the diagnostic. I have a 16 plate w205 220d coupe. I’ve had the car 4 months and so far it’s been nothing but a money pit! Constant issues. I was told today by the dealership that I was mad for buying a diesel as I just drive around town and I will have constant problems with it and eventually I will need a whole new dpf which is 2 and half grand on my car. Im Someone who don’t know much about cars and was naive to think that buying a £17,000 car for mostly local driving will end up causing me problems. All you wanna hear after spending that much on a car.

 

[Rhino51]

If your car has always been serviced by Mercedes then it would be worth giving them a call. The worst they can say is no.

However, if there’s an air filter sensor activated it sounds very much that servicing hasn’t been carried out correctly because this is one of the routine replacement items. It’s something you can do easily yourself. You could probably get a cheapish version from Halfords or on eBay but I would recommend the genuine part from your nearest MB dealer. It’s never worth skimping on such things.

As for the NOx sensors, you have to be very careful buying them yourself. There are still lots of the original ones around for sale that will soon fail again. The genuine replacements are a later design, that’s hopefully more reliable. But even they need the software updating when they’re fitted to ensure they don’t give false results. A good MB Indy can do the job for you a bit cheaper than MB, but the parts are really expensive so you won’t save much. If they say they can do it a lot cheaper there’s a good chance they’re using the old style sensors. I’m afraid that your best option will be to get them replaced by MB with your warranty covering some of the cost.

You can carry on using the car without any problem for a short while. The sensors are just telling you that things have gone a little bit out of the normal range. You won’t do any damage to anything by driving a few hundred miles with the yellow warning light on. Just don’t leave it too long or your DPF could get damaged and that’s another big expense.

Hi,
I’m having the same problems with my MB ,
Can you tell which department and number you called.
I’ve already sent an email but so far I’ve had no reply.
Thanks

 

[wongl]

Just sharing my experience, a month ago my fuel relay unit went then 3 weeks after that my ad blue injector was blocked, then last night my engine management light came on showing fault code po4020 catalytic converter, took it to Mercedes Maidstone today and was told both Nox centres need replacing at £430 plus vat each and 2 hours labour. The dealership said don’t worry we are going to make a phone call to MB head office, she came back 10 minutes later and informed me MB are going to pay 100% of the bill and the diagnostic. I have a 16 plate w205 220d coupe. I’ve had the car 4 months and so far it’s been nothing but a money pit! Constant issues. I was told today by the dealership that I was mad for buying a diesel as I just drive around town and I will have constant problems with it and eventually I will need a whole new dpf which is 2 and half grand on my car. Im Someone who don’t know much about cars and was naive to think that buying a £17,000 car for mostly local driving will end up causing me problems. All you wanna hear after spending that much on a car.

Did you buy your car from a car dealership, or better still as an approved used car from an MB dealership? If you did you would probably have a used car warranty which may cover some/all of the faults you experienced? If not, I suggest you call MB and purchase an extended warranty off them.

I have a C300h of the same vintage as your 220d and took out a two-year MB extended warranty for £850 when the original manufacturer's warranty expired in December. For the complex hybrid C300h, I think this is a very reasonable price for two year's insurance.

 

[Deleted member 151559]

Hey all the petrol 204 C350 has this NOX sensor issue too.

Knighterrant above has had his done, mine were done last year (before I bought it thankfully) and I just heard of another w204 c350 petrol needing them.

Hopefully this was a poor quality sensor and the new ones supplied are better.....If it goes again on my car in 7 years time it might well write it off! Ridiculous.

 

[Deanw23]

Did you buy your car from a car dealership, or better still as an approved used car from an MB dealership? If you did you would probably have a used car warranty which may cover some/all of the faults you experienced? If not, I suggest you call MB and purchase an extended warranty off them.

I have a C300h of the same vintage as your 220d and took out a two-year MB extended warranty for £850 when the original manufacturer's warranty expired in December. For the complex hybrid C300h, I think this is a very reasonable price for two year's insurance.

hello buddy, I brought my car from car giant in London and to be fair they have paid for everything apart from the full service I put it through. But I never in my life thought my car would be in the garage so much buying a 17k Mercedes only done 26000 miles. That’s great advice mate ! I didn’t know you could buy the extended warranty what does that cover ? £850 is reasonable I would say mate. Same vintage as your c220d what do you mean by this lol ?

 

[Rhino51]

Thanks for the very quick response.

I appreciate that.

Based on what I read here, I called Mercedes. They were polite and said that I would need to take it into an authorised Merc service centre near me, who would then run a diagnostic test (another £144!) - and then perhaps (perhaps maybe - just maybe) - they might offer to cover a part of it.

Obviously, getting it done by an authorised service centre would be even more expensive and then on top, there is the additional cost of getting another diagnostic done.

You might be right: it might be best to bite the bullet and go with it.

I wonder if the independent company that I got the original diagnostic done from is using the new or the older design. I do have the part numbers:
A0009051512 (Nox sensor) - as recommended by the independent German service centre
A6510940100 (air filter)

Is there a way to determine if the sensors recommended above are the upgraded ones?

Also, is it necessary to replace both Nox sensors if only one is gone? I suppose this is just for precaution.

What do you think?

Thank you once again!

Can faulty Nox sensors be removed , cleaned and reused ?
I’ve been watching some guys online showing how to remove and clean the sensors rather than replace with costly replacements.
What would be a reasonable price pay for new ones, labour, how long, plus any other related work .

 

[Deanw23]

Can faulty Nox sensors be removed , cleaned and reused ?
I’ve been watching some guys online showing how to remove and clean the sensors rather than replace with costly replacements.
What would be a reasonable price pay for new ones, labour, how long, plus any other related work .

read the thread lad it says how much people have paid for 2 Nox sensors and labour!

 

[Deleted member 65149]

Hi,
I’m having the same problems with my MB ,
Can you tell which department and number you called.
I’ve already sent an email but so far I’ve had no reply.
Thanks

Sorry for the delay responding, I haven’t checked in for a while. Send me a PM and I’ll reply with the details. I tried sending them to you but your privacy settings wouldn’t let me.

 

[Deleted member 65149]

Hey all the petrol 204 C350 has this NOX sensor issue too.

Knighterrant above has had his done, mine were done last year (before I bought it thankfully) and I just heard of another w204 c350 petrol needing them.

Hopefully this was a poor quality sensor and the new ones supplied are better.....If it goes again on my car in 7 years time it might well write it off! Ridiculous.

I also hope the new ones last.

 

[Deleted member 151559]

I also hope the new ones last.

I heard they are a different part number and the car needs a software update to deal with them. So they sound substantially different.

 

[Deleted member 65149]

I heard they are a different part number and the car needs a software update to deal with them. So they sound substantially different.

That’s my understanding too. Just keep our fingers crossed.