Fault Code 912749 The air quality sensor has a malfunction. There is an internal electrical fault.

[Borris1954]

My new to me 2017 W246 has this fault code which I can clear but it reappears within a few miles so I need to replace the sensor.

I understand the sensor is mounted in ventilation air intake stream in front of the windscreen and it's function is to switch on air recirculation if there is excessive pollution (Nox) in the incoming air.

Has anybody replaced one of these? WIS doesn't seem to cover this. Is it accessible without pulling the wiper arms and open up the plenum chamber/air/water channel?

Thanks

 

[Borris1954]

I scanned the car with SDS again yesterday after doing a service and this stored fault code had reappeared (I have yet to see it as an active code). So I took off the wiper arms and the below the screen plastic panel to have a look for this sensor but you still can't see it. As I was short of time I just put it back together for now but it looks like I need to take out the wiper motor assembly and then remove the top part of the plenum chamber to find it. A job for another day. It's very strange WIS doesn't seem to cover changing this sensor or if it does I haven't found it yet,.

 

[BRONX92]

Hey buddy, I am about to buy a car with this error code also the dealer is replacing the sensor but how serious is this code and did you sort it?

 

[BRONX92]

@Borris1954 ^^^

 

[Borris1954]

Sorry did not spot your question. No it's still not fixed as I haven't found the sensor yet! Even did a text based search of WIS for my VIN and it is totally silent on instructions to replace it.

As far as I can see unless you drive through long tunnels or in heavy smog conditions it's not a great issue. You can always just put air recirculation on manually.

But if anyone can point me in the right direction I will put in the replacement sensor I have had here for over a year. My fear is it's a dashboard out job so not worth the effort.

 

[mcaptur]

Same problem.. Where is sensor located? woudl like to replace it..

 

[HarleyMYK]

I am in California with a 2017 B250e. I was told buy a third party shop that specializes in these that the whole dash would need to come apart and it is difficult to get at so about $500 US for labor. We are just living with the error message for now.

 

[ALFAitalia]

Mercedes like to make stuff difficult.... on my ALFA it was on the slam panel.