PaintedQuail

Was on a road trip and after a gas stop CEL came on. At dealership next day, it showed fault codes 300 and 121 for upstream and downstream NOx sensors needing replacement. Cleared codes, immediately came back on. Needed my car, so agreed to come back in as soon as the starts remaining countdown came on. Got a new tank of diesel in town (18 gal), and CEL went off the next day and has been off since (1 week).

Has anyone ever seen this with their Bluetec? We're thinking it could have been a bad tank of diesel and that rather than failing, the NOx sensors actually sensed it..... and then sensed when the clean diesel was put in, turning off the CEL. Am I reaching and we should just get the NOx sensors cleaned or replaced? Thoughts? Thanks!

Kartergreg

Last year I had the fault code for upstream and downstream NOx sensors, P0229 code. The P0300 and P0121 do not apply to NOx sensors.

Something is off in your story....

PaintedQuail

Hmmm. Well, CEL came on - went to the dealer, the paperwork says:

"scan for fault codes - found stored code only for NOX sensors (2) - clear codes and reset systems. If light comes back on both nox sensors will have to be replaced - estimate $1800."

I asked what the codes were and they said 300/121. I said not a P code? They said no, just 300 and 121 (not P0300 and P0121 as you said above). CEL immediately came back on, but went off the day after we got new gas.....

Service Mgr said he was not surprised that the CEL went out, but that the NOx sensors would both still need to be replaced at some point..... Just curious to me that BOTH would "fail" simultaneously, upstream and downstream if it wasn't something like bad fuel.... but what do I know? :-)

Koenig1

I, too, on a trip to FL last winter, discovered the pain of failed NOX sensors. Fortunately, the Ft Myers dealer replaced them under warranty... mine is a 2015. I was armed with all sorts of data that the NOX sensors are part of the Emission Warranty(8yrsI believe), but didn't have to argue! Not sure as mine was still under its orig warranty?? My sense was the same as yours, bad fuel purchased somewhere on the trip south..... glad yours 'recovered'! $1800 for 2 sensors???? It didn't take the dealer much time to replace mine and.... wash the car... LOL!

marchgroupinc

Can you tell me what data you have to show that the NOX sensors are covered under Emissions warranty in Canada. Mine is 2014 with 100,000 and MB says not in the warranty only DPF, Engine control Unit and instrument cluster are covered. I thought anything needed to pass emissions test was covered for 8 years 130,000 km but cannot find documentation on that. Any help proving that is appreciated.

Koenig1

Well, I don't have all the data that I hiked into Fort Myers with, but, I was still under my initial warranty. I also have and Extended Limited Warranty. All that said I went into MB Canada website and browsed through their warranty statement. As you can see some emmissions are covered for 2yr/40K, while others are for 8yr/130k. Now I was definitely over 2yrs, and had about 65k kms, so I'm not sure how they work it??? I have included a PDF of my bill. Note: the mileage is in miles(US). Hope that helps

New Car Warranty

• 

Koenig1

Double Post