Snatched and rolled up, Nox Nightmare

[TigerDrummer]

Greetings to all,

This is my first post, but I've been a lurker here for quite some time. Because this forum has been an absolute treasure trove of helpful hints, I'm coming to you for assistance.


My second W212, after upgrading from a 220 Bluetec, was purchased around three weeks ago; the model is the 2016 E350 Bluetec. I adore the platform and could picture myself driving this car indefinitely, but suddenly the dreaded Nox problems have surfaced. The low mileage of the car (about 55,000 miles from new) likely clogging up the sensor. This led to a malfunctioning sensor 2 (following scr) and an Adblue gauge that is currently reading 400 miles.

I figured I'd give it a go today to replace the sensor that I bought for a pitiful £175 on eBay. The nut hasn't budged an inch, and I've gotten a little closer after seven hours of perspiration, cursing, bleeding, and shivering on the road.

I used the standard fare of penetrating fluid, a Nox sensor socket, and some manual labour, but to no avail. Proceeded to mapp torch, but got nowhere. Shocking it, turning it crimson, and then submerging it in icy water. Completely nonexistent. I used a Nox socket, a 22mm spanner, a pipe wrench, a hammer, and a chisel, but none of them worked.

I have exhausted every available daylight and profanity, so tomorrow I will try again. As a last option, I will use a 6-sided impact socket to cut the sensor immediately above the nut. Going at it with a breaker bar as there isn't enough space to get an impact driver.

Is anyone else thinking of doing anything else before I rip the bung, cut the threads, or blow my exhaust?

[Lemmand]

To remove sensor connections and the like, it's best to cut them off flush with the nut. This will allow you to use a six-sided socket, which offers six points of contact instead of just two when using a spanner.

In any case, it's chop, drill, tap.

[TigerDrummer]

I'm going to test it out tomorrow and see how it goes. The threads will be inevitably messed up by me. Is anyone familiar with the bung's thread pitch? I will then apply a thread chaser to it.

[HolyRoach]

Apologies for the trouble you encountered when removing the NOx sensor.

By the way, did you purchase the vehicle from an individual? That is, there is no legal guarantee to rely on?


Indeed, I am.Am I to understand that you determined the AdBlue problem to be caused by a malfunctioning NOx sensor? Is an MB scanner in your possession? Also, did you know that updating the software would be necessary while replacing the NOx sensor?

Some private dealers have been unscrupulous, which is why I am asking.recognised for their attempt to cover up costly AdBlue flaws for a short time before selling the vehicle to an unwary buyer. You should definitely get the problem checked out before you shell out any cash, even if there's no turning back once it's a private sale.

[TigerDrummer]

Hey there, buddy! I'm afraid you're quite right. The very cheap price for a premium plus with relatively few kilometres makes me think you're right, but I was ready to face the repercussions of the private sale nevertheless.

Yes, I did scan it with an iCarsense MBv4.0 in regards to the malfunction. At first, it returned the P229F error code for Nox sensor 2 in bank 1. I hoped it was because the car had been sitting in the cold for a while, so I cleared it. The dreaded Adblue countdown was triggered three days later when the issue returned.


I will do the diagnostic procedure on the same tool as the Nox and Adblue, and hopefully it will fix it. I will then blast it down the highway.

I appreciate your response.

[Dudeta]

A plethora of issues, including bad fuel usage, decreased power, more nox difficulties, etc., were reported after the diesel update was applied by MB.

[bellox]

Unlike a lambda sensor, which uses a threaded bung, this one uses a pocket. The tube nut firmly presses down on the sensor as it rests on its ridge. On occasion, they do get seized very badly. By removing the flange and replacing it with a piece of an appropriate big nut that has the correct thread, I have achieved success in the past. After you've positioned it squarely in the hole and loosely on the tube nut, you can tack weld the thin slice into place. Full welding isn't necessary because it won't seal there; instead, the ridge on the probe will do the sealing. Not easy to describe.

[TigerDrummer]

It has the MB dealer history up until 2021 and the specialist history after that, although I'm not sure if the car has actually had it. What was the release date of the update?

[TigerDrummer]

It seems to me that the teach-in approach entails installing a new Nox sensor, teaching it the necessary parameters, and then relearn the Adblue values. Does the Adblue need to clear codes and be driven on a quality highway before it realises it's working?