EML light - NOX sensor

[fizagaren]

Hi all,

I have purchased a glc 2 weeks ago and the EML came on last week

Took to the garage, and the confirm that it could be a faulty box sensor.

I will be rejecting the car. However they want me to drive to the dealer for their own tests.

Will the EML light stay on until the sensor is replaced / error cleared ?

Or is the a certain time period /number of stop/start cycles that can occur for it to clear automatically ?

What I don't want is to drive and hour for the light to vanish

Thanks

 

[BlackC55]

Why reject it for just a sensor issue? Its easily fixed. There are lots of sensors that can go wrong at any time and often do.

 

[BlackC55]

The light will go off when the sensor is replaced and the codes are cleared. It may need software too. Use only a genuine (latest number) NOX sensor

 

[W1ghty]

Hi all,

I have purchased a glc 2 weeks ago and the EML came on last week

Took to the garage, and the confirm that it could be a faulty box sensor.

I will be rejecting the car. However they want me to drive to the dealer for their own tests.

Will the EML light stay on until the sensor is replaced / error cleared ?

Or is the a certain time period /number of stop/start cycles that can occur for it to clear automatically ?

What I don't want is to drive and hour for the light to vanish

Thanks

The light will have logged a fault within the cars memory, even if the dashboard eml goes out .
It’s obviously up to you if you reject the car, but if it’s run with no issues for 2 weeks (I’m guessing the car isn’t new) . Then faults do happed with cars .
Who is to say the next car you buy then gets a fault at 3 weeks , what will you do then ?
Do you have a Mercedes Mobilio breakdown cover , they will attend and tell you what the fault is .

 

[MSG2004]

The light will have logged a fault within the cars memory, even if the dashboard eml goes out .
It’s obviously up to you if you reject the car, but if it’s run with no issues for 2 weeks (I’m guessing the car isn’t new) . Then faults do happed with cars .
Who is to say the next car you buy then gets a fault at 3 weeks , what will you do then ?
Do you have a Mercedes Mobilio breakdown cover , they will attend and tell you what the fault is .

Agreed
Depends if vcar bought from MB and if so, I would not reject it if the car was otherwise good, ie unmarked, lots of tyre tread and disc/brake life etc, not smoked in or pets and the right spec and colour.

Let's say you changed your car for another used car, it may have more problems. Personally, I'd give them a chance and if the car has Mobilo, call them out they will diagnose and or fix it and then They can even book the car in for you and that happened to me got it booked in next day - ie nox problem and got a half decent loand car, an E class, mine is gle - they sorted everything in three days.

 

[OneForTheRoad]

Wait till the front wheels start banging on full lock in the cold on slow turns . . A failed nox sensor is nothing . The glc is a class act tbh . Don't let a daft sensor put you off . They eat up motorway miles in pure comfort.

 

[TC350]

With a £25 OBD2 scanner you can cancel the error (and thus EML) yourself. Mine comes on with the Nix sensor failure code roughly once a year. I cancel a couple of times over the next week or so and then it stays off.

I have little or no faith in the sensors really failing. I feel that instead it's either more of a case of a bit of sh1t on the sensor that eventually gets blown off, or the unnecessarily tight limits saved in the software being temporarily exceeded. Just because "the computer says no" doesn't mean that something needs replacing. It's a nice little earner for a few people though.

 

[Uky]

Repeating some information I got from a MB mechanic a few years ago:
A common cause of NOX-sensor failure comes from condensated water in the end muffler.
The water builds up to quite some amount. If and when the driver presses the brake pedal
some of the (cold) water rushes forward and hits the (warm) NOX-sensor causing it to crack.

Mercerdes issued a service message: A 3mm diameter hole should be drilled in the rear muffler
at its lowest point. This will let condensated water to leak out while not affecting the rest
of the system.

I did that on my petrol car. Quite a poodle formed on my garage floor...

 

[OneForTheRoad]

Repeating some information I got from a MB mechanic a few years ago:
A common cause of NOX-sensor failure comes from condensated water in the end muffler.
The water builds up to quite some amount. If and when the driver presses the brake pedal
some of the (cold) water rushes forward and hits the (warm) NOX-sensor causing it to crack.

Mercerdes issued a service message: A 3mm diameter hole should be drilled in the rear muffler
at its lowest point. This will let condensated water to leak out while not affecting the rest
of the system.

I did that on my petrol car. Quite a poodle formed on my garage floor...

Ive got a cavapoo , love him .

 

[Uky]

...Should have been p u d d l e ...

 

[OneForTheRoad]

Ive got a cavapoo , love him .

Im trying to get my head around your theory , and the positioning of the nox sensors coming into contact with water in the exhaust. It would take something short of a tusammi for water to reach most Nox sensors . An oxygen sensor maybe ,but not a Nox. Certainly not on my om642 . Water simply cannot climb up . I've read about moisture forming on the tips of Nox sensors from short journeys,but not from being splashed by braking hard.

Most petrol engines spew out water when revved anyways at any given time .

 

[Uky]

I agree but then MB would not likely issue such a recommendation unless they
had experienced this. But - If the service bulletin was for a specific model or
adressing the problem in general I do not know. I drilled holes just to be
on the safe side. A significant amount of water came out.

 

[Skd884]

Sell the DIE sel and purchase a petrol/ev car.

 

[OneForTheRoad]

Sell the DIE sel and purchase a petrol/ev car.

A nice beige one maybe

 

[OneForTheRoad]

I agree but then MB would not likely issue such a recommendation unless they
had experienced this. But - If the service bulletin was for a specific model or
adressing the problem in general I do not know. I drilled holes just to be
on the safe side. A significant amount of water came out.

Pretty sure they Did this in the 80's when Nox sensors weren't even around on petrol cars. Prevented the back boxes rotting from inside out , when metal was like tissue paper , back in the day .

 

[ALFAitalia]

Lots of car used to have silencers with drain hole back when I was selling new cars.......so that's 87 to 03....God I feel old!! You used to see water dripping from the holes, when sat behind them in queues, on cars that had only recently been started.