x35D P122C OBD2 code - which NOX sensor?
 

I have a P122C code on my 2009 X35D which points to a NOX sensor short circuit.

Since there are two sensors, does anyone have a clue which might be the problem? I'd normally replace both but they're $600 per sensor. (ouch)

Would the IPNA software be able to isolate this better than a generic ODB2 reader? I don't have a windows laptop to install the software but if it will isolate it, I'll be money ahead.

thanks.

Ista-p/rheingold works and has test plans and the ability to calibrate the new sensor. Look on cartechnology forums for it

Took me forever to find info to setup Rheingold. So, once I figured all out, documented here.

And, if you end up needing a NoX sensor, PM me. I have got a couple used ones, one less than 15K miles on it.

As I investigate, another question comes to mind.

Why would I get this code only when pulling a trailer? Once I wasn’t pulling a trailer, the Dash light is no longer active.

Sensors have an operating range. So it's possible that you have a sensor that is reading faulty (either higher or lower than it should be) but still be within that operating parameter. Therefore, no code is generated.

When you're towing, you're changing the operating conditions of the engine with a much higher load. If in these conditions, the NOx sensor at a particular time is supposed to be reading somewhere between X and Y value, and it pops up with Z value because the higher load makes it read OUTSIDE of it's operating parameter, it will pop up a code at that time.

It sounds like you have a sensor that is on it's way out, but so far only high-load conditions force its readings outside of normal range. At some point, it will do it consistently.

+1 on above.

Hmmm. Ive seem some descriptors that this is a fault in the heater circuit... ie its a continuity fault, NOT an operational range fault.

http://autodiagcart.com/wrd/wp-conte...-2009-2010.pdf

Could be a connection to the sensor. Worth a few wiggles.

This doesnt explain why it shows when towing.

My 2 cents

You have a point. Code P122C is identified in Rheingold as having to do with disconnection or a short.

Thanks for the information. That’s good stuff! If nothing else it points to the front sensor which is what I needed but didn’t have any software set up to tell me.

As I skim through nearly 300 pages of computer monitoring crap and all the things that can become an issue, it makes me seriously consider the pdf/scr/egr delete. I’m at 131000 miles and at some point the sensors will cost more than the car is worth. 😊

ABC deletes seem to move "system weakness points" to other parts. In my (and another user here, at least) delete put additional load on injectors, causing at least one to go out of spec.

Honestly, I'd recommend just replacing the malfunctioning NoX sensor now and postpone for ABC delete until something big in emissions components starts failing to make it worth spending $ on deleting.

I'd almost recommend the opposite as I'm currently preparing to have the ABC delete done.

After pricing out the cost to replace the upstream NOX sensor. Then hearing it from a number of mechanics stating once the upstream goes the downstream is likely right behind it. Not to mention having a brand new upstream and an old downstream could cause a missmatch in readings..... They essentially all recommended to replace both at the same time. The cost to change both was as much or more than the cost to do the delete.

I should note that I'm also somebody that if I'm going to spend that much money on something, I want it to give me something better than I already have not bring me back to where I was.

You have a point there, but a good used NoX sensor can be had for tiny fraction of new. With so many people performing deletes, these sensors are no longer such a commodity.
Also, I had success ultrasonic-cleaning in one of my NoX sensors last year to restore its functionality.

P.S. Join NABDOG group on Facebook.

While I was struggling to find someone willing to do the labour on the delete I was contemplating buying some used NOX sensors, but the thought of there being no guarantee and maybe the used ones letting go 6 months down the road wouldn't leave my head.