LesF

Since my last post I've had 2 more NOx sensor failures. The latest last week. Interestingly all four have been replaced but no sensor location has failed twice.

Luckily all the issues have been fixed at no charge since everything is covered under the warranty. The dealers retail replacement per sensor is $445.00

rick8560

Update: I now have about 26,300 miles and I am going for the "A" service in about 2 weeks. I have not had another episode of the dashboard warning of x# of starts left due to the AdBlue situation. The first time it happened, they just added the fluid first but the sensor would not correct itself. They replaced the sensor and still had problems. I don't remember exactly what they did as it was well over a year ago, but they kept the car for several days supposedly troubleshooting it.

KyKen

I had been reviewing this thread for a few years but I wanted to share a post.

I bought the GLK250 used and the dealer repair history showed there was a repair for the NOx sensors. After reading this thread, I assumed the issue was fixed according to Mercedes Warranty repair. The odometer was around 10,000mi.

I next encountered an issue at 17,000 mi with a trip to the dealer to fix both NOx sensors and get me on the road.

Well, this morning I am back at my dealer with 35,000 miles and first the CEL came on with a P229F, and 20 miles later, the AdBlue Indicator came up in the cluster indicating low DEF. I added about 2+ Gallons of DEF to top it off and it still stayed on. With 6 starts left, I drove it to the dealer.

I don't think the technician knows the issue. Still under warranty!

Alex Bel

Keep us updated whether this is sensors problem.
Maybe the indicator has to be reset.

gmcop1

2014 GLK250 with 42,000 miles. Check engine light on. Dealer says bad oxygen sensors not covered by emissions warranty. What good is the emissions warranty?

andreigbs

3 year-old thread bump, eh?

Sorry to hear of your troubles. Unless you have a good relationship with your MB dealer, I'd suggest trying a different MB dealer. These are common faults in the Bluetec emissions system and there are updated parts available. From my reading here, the replacements have held up well.

You could also visit a trusted Indy shop that works on German cars (and has MB specific scan tool) to have these sensors replaced for a fraction of what the MB dealer charges.

Or you could find a software tuner in your area and have the ECU "optimized" into passive off-duty mode, no more problems.

gmcop1

Thanks, will try the tuner approach.

woonwoon

​​​​​​I got my 2014 glk rear nox sensor replaced at the dealership less than 2 months ago, cost me nearly $1700, now the start limitation countdown back on again. (Vancouer Canada)

Diabolis