NOx sensor torque settings for m276

[MercC350Coupe2011]

Hi all,


I have got a Mercedes C350 2011 m276 engine. I have got a NOx sensor issue and I am going to change it myself. I have got two questions.

Does anyone know the torque settings of the NOx sensor 3 ? Does it need STAR programming or just put it clear the error and I am good to go?

thanks in advance.

 

[Tuercas viejas]

Yes rule of thumb.
With the threads chased out & clean, run the sensor in to "seat it then 1/2 turn. 1/3rd turn on re-using one.
or use NGK O2 sensors guides who were called in by MB to get it (NOx sensors) "right "since the body is the same :-
. Torque to proper specs as below:

• M18 sensors (sensors with 18mm diameter threads) - Install finger tight then 1/2-3/4 turn with wrench / O2 sensor socket 26-33ft. lbs.
• M12 sensors (sensors with 18mm diameter threads) - Install finger tight then 3/4 - 1 turn with wrench / O2 sensor socket 13.2 -17ft. lbs.
• Don't go mad or force anything, remember the old RN expression steady as she goes, tight is tight and too tight is over tight because you are crushing a sealing washer on NEW sensor

Yes you will need to SCN code them in with what you call a Star but some independents use Autologic who have remote wifi program support to do this for a fee. .

Andele pues
Amistades
Tuercas viejas

 

[MercC350Coupe2011]

Yes rule of thumb.
With the threads chased out & clean, run the sensor in to "seat it then 1/2 turn. 1/3rd turn on re-using one.
or use NGK O2 sensors guides who were called in by MB to get it (NOx sensors) "right "since the body is the same :-
. Torque to proper specs as below:

• M18 sensors (sensors with 18mm diameter threads) - Install finger tight then 1/2-3/4 turn with wrench / O2 sensor socket 26-33ft. lbs.
• M12 sensors (sensors with 18mm diameter threads) - Install finger tight then 3/4 - 1 turn with wrench / O2 sensor socket 13.2 -17ft. lbs.
• Don't go mad or force anything, remember the old RN expression steady as she goes, tight is tight and too tight is over tight because you are crushing a sealing washer on NEW sensor

Yes you will need to SCN code them in with what you call a Star but some independents use Autologic who have remote wifi program support to do this for a fee. .

Andele pues
Amistades
Tuercas viejas

Thank you for your response.

The SCN code is quite interesting fact that I didn't know. Let me ask you then a few things.

I had a bad NOx sensor at bank 1 some time ago. I found one almost brand new and it was changed by an independent garage. He prossibly only erased the errors. After 500 miles I got an error message again saying bank 2 NOx sensor was bad. I found a used NOx sensor on ebay and I changed it on the same independent garage (possibly he doesn't have star or he didn't mention anything). After 500 miles I got the same error at bank 2 again. I got another NOx sensor and I was about to change it today with a friend but the torque wrench didn't fit in so I need to take an offset lamda socket. However if it needs programming even if I change the sensor I might take the same error again? Do you know how much a dealer will need for programming them?

 

[MercC350Coupe2011]

by the way does anyone know if I use this offset socket how much dirrence I have in torque? It should possibly give a little bit more torque than the torque wrench due to the offset.

 

[Tuercas viejas]

Thank you for your response.

The SCN code is quite interesting fact that I didn't know. Let me ask you then a few things.

I had a bad NOx sensor at bank 1 some time ago. I found one almost brand new and it was changed by an independent garage. He prossibly only erased the errors. After 500 miles I got an error message again saying bank 2 NOx sensor was bad. I found a used NOx sensor on ebay and I changed it on the same independent garage (possibly he doesn't have star or he didn't mention anything). After 500 miles I got the same error at bank 2 again. I got another NOx sensor and I was about to change it today with a friend but the torque wrench didn't fit in so I need to take an offset lamda socket. However if it needs programming even if I change the sensor I might take the same error again? Do you know how much a dealer will need for programming them?

A lengthy answer here.
Question #1 How was it determined the upstream NOx sensor was bad ?
OK I understand they have gone through about 4 iterations that I know of on this side but the ultimate latest & greatest has an NGK sensor tip in it connected to a Bosch solid state box half way up the cable which makes its own computer page for want of a better description. On the back of the box the question is what is the part number?
Lets assume the replacement it was good and the original was bad, but it needed SCN coding anyway post install to start shaking hands with the ECM thus speaking the right language .
Now once installed the tech needs to drive the vehicle for about 30 miles to see if the car is re-genning automatically and that the upstream NOx sensor is transmitting NOx info in LIVE DATA..
If there is next to no tangible signal there is a likelihood of an air leak into the "zorst system upstream, or the Cat is plugged up. Then test the pressure readings on the EBP and diff pressure sensor in HPa.
So its at that point you return to the shop and investigate why!.
Question/statement #2.
When doing the road test and upstream is seen working what is the rear NOx sensor doing?
Reading off the two figures do a quick calculation and there MUST be at least a 50% of reduction across the SCR cat when the system is seen working .
New sensors and an SCR cat will give more than 75% reduction.
In our case we touch the scan tool and print off the figures as you drive with an assistant proving at least its working.
Seems from your narrative that the two sensors were not SCN coded and after a set of drive cycles the system "sees" that it not speaking the right language to communicate.
Its a bit like trying to date a drop dead gorgeous foreign female and and you cannot speak her lingo with any fluency. Confusion exists ! OMG opportunity lost Mr Smoothy !

Statement & question #3
For the system to reduce NOx it MUST have Adblue DEF fluid pumped into it when required.
So was the DEF pump tested by a bi directional scan tool to confirm that fluid is actually injected into the SCR cat .The pump must generate 5000HPa be capable of backing off the pressure by the return system and see an operating pressure of around 3600 HPa.
These things are vital as well ,as checking the atomized delivery of DEF fluid through the dosing injector which must not be furred up with crystals of DEF AND that it is of the correct specific gravity .

Now the practical
Yes an O2 socket will fit. Cranked is better and use a good length knuckle bar , don't tickle it !! '
When I know that the sensor is junk I sometimes simply cut the harness at the tip, and and use a double depth 1/2" socket to drop over the top of the sensor to work it out.
Penetrant like Plus Gas might be needed as well as a plumbers MAP gas torch to heat the boss area to make removal a bit easier if its bound up .
Once installed a shop should charge you about???? --well over here I charge $ 250 for the programming and the road test to certify its system functionality and the test print outs go to the customer ands archived on the finished R/O.
Hope that gives you some insight
.All the best
Tuercas Viejas

 

[Tuercas viejas]

by the way does anyone know if I use this offset socket how much dirrence I have in torque? It should possibly give a little bit more torque than the torque wrench due to the offset.

View attachment 110809

I/We have both
The squared fitting one is good BUT when things are in a tight area the other is very useful so that you can get a swing on it .
TV

 

[MercC350Coupe2011]

A lengthy answer here.
Question #1 How was it determined the upstream NOx sensor was bad ?
OK I understand they have gone through about 4 iterations that I know of on this side but the ultimate latest & greatest has an NGK sensor tip in it connected to a Bosch solid state box half way up the cable which makes its own computer page for want of a better description. On the back of the box the question is what is the part number?
Lets assume the replacement it was good and the original was bad, but it needed SCN coding anyway post install to start shaking hands with the ECM thus speaking the right language .
Now once installed the tech needs to drive the vehicle for about 30 miles to see if the car is re-genning automatically and that the upstream NOx sensor is transmitting NOx info in LIVE DATA..
If there is next to no tangible signal there is a likelihood of an air leak into the "zorst system upstream, or the Cat is plugged up. Then test the pressure readings on the EBP and diff pressure sensor in HPa.
So its at that point you return to the shop and investigate why!.
Question/statement #2.
When doing the road test and upstream is seen working what is the rear NOx sensor doing?
Reading off the two figures do a quick calculation and there MUST be at least a 50% of reduction across the SCR cat when the system is seen working .
New sensors and an SCR cat will give more than 75% reduction.
In our case we touch the scan tool and print off the figures as you drive with an assistant proving at least its working.
Seems from your narrative that the two sensors were not SCN coded and after a set of drive cycles the system "sees" that it not speaking the right language to communicate.
Its a bit like trying to date a drop dead gorgeous foreign female and and you cannot speak her lingo with any fluency. Confusion exists ! OMG opportunity lost Mr Smoothy !

Statement & question #3
For the system to reduce NOx it MUST have Adblue DEF fluid pumped into it when required.
So was the DEF pump tested by a bi directional scan tool to confirm that fluid is actually injected into the SCR cat .The pump must generate 5000HPa be capable of backing off the pressure by the return system and see an operating pressure of around 3600 HPa.
These things are vital as well ,as checking the atomized delivery of DEF fluid through the dosing injector which must not be furred up with crystals of DEF AND that it is of the correct specific gravity .

Now the practical
Yes an O2 socket will fit. Cranked is better and use a good length knuckle bar , don't tickle it !! '
When I know that the sensor is junk I sometimes simply cut the harness at the tip, and and use a double depth 1/2" socket to drop over the top of the sensor to work it out.
Penetrant like Plus Gas might be needed as well as a plumbers MAP gas torch to heat the boss area to make removal a bit easier if its bound up .
Once installed a shop should charge you about???? --well over here I charge $ 250 for the programming and the road test to certify its system functionality and the test print outs go to the customer ands archived on the finished R/O.
Hope that gives you some insight
.All the best
Tuercas Viejas

thank you very much for your lengthy answer but I think you wrote a few things for diesel engines. My car has a petrol V6 3.5 litres engine. Does it need SCN coding as well?

 

[Tuercas viejas]

thank you very much for your lengthy answer but I think you wrote a few things for diesel engines. My car has a petrol V6 3.5 litres engine. Does it need SCN coding as well?

In short No
.TV

 

[MercC350Coupe2011]

In short No
.TV

Hello mate. Coming back to the same question. Are you sure that the Nox sensors of this petrol m276 engine do not need any kind of ECU updating or SCN coding? If I change the sponsors and just delete the fault codes I should be good to go?

I am asking this question again because I have changed two Nox sensors ( second hand from eBay to be honest) and I was having problems. Finally went to Mercedes and they told me that they need coding but I got the fault codes back up after a few miles. Just wondering if I try to swap the Nox sensors myself ( in bank 1 is working) and see if in bank 2 the Nox sensor is the problem or something else.

 

[Sheeple]

Hello mate. Coming back to the same question. Are you sure that the Nox sensors of this petrol m276 engine do not need any kind of ECU updating or SCN coding? If I change the sponsors and just delete the fault codes I should be good to go?

I am asking this question again because I have changed two Nox sensors ( second hand from eBay to be honest) and I was having problems. Finally went to Mercedes and they told me that they need coding but I got the fault codes back up after a few miles. Just wondering if I try to swap the Nox sensors myself ( in bank 1 is working) and see if in bank 2 the Nox sensor is the problem or something else.

did you ever get the answer you were looking for? I'm in the exact same situation with the same engine and I've changed my upstream nox sensor twice only for the same error codes to come back a few miles later both times, I don't want to have to take it to the stealership