# Service Emissions System Message & Codes



## MP81 (Jul 20, 2015)

A few months back, the car threw a sudden "Service Emissions System" screen while my wife was driving - only 175 miles until the speed limit drop, too. Then it went away on its own.

We were driving home from lunch and it suddenly popped up on me today. I felt the "See owners manual now" was a nice touch - a little hard to do while I'm driving, no?

Anyway, I wanted to make sure I got the codes this time, as they were already gone last time. The P11DC is one we've had for a month or so now - NOx2 sensor, because of course that can only last just over a year (in other words: just after the warranty on the sensor was up - better yet, _just after_ I purchased this one, they increased the warranty to 24 months - up from the 12 months of this one).

I cleared all the codes and the message went away - my wife drove to the store and back later, and it doesn't appear to have come back.

Thoughts on this one - there's a good few codes there.


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## MP81 (Jul 20, 2015)

Bump - wife just messaged me saying the 175 mile/Service Emissions System/Read Owner's Manual Now (while driving) just popped back up.

I imagine it'll be the same codes.

Thoughts? The NOx2 reading looks absurdly high - shouldn't it be lower? Could be causing it?


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## MRO1791 (Sep 2, 2016)

MP81 said:


> Bump - wife just messaged me saying the 175 mile/Service Emissions System/Read Owner's Manual Now (while driving) just popped back up.
> 
> I imagine it'll be the same codes.
> 
> Thoughts? The NOx2 reading looks absurdly high - shouldn't it be lower? Could be causing it?


If the NOx is higher on sensor 2, than sensor 1, that is illogical, it means your SCR/DEF is making NOx, exactly the opposite of what it was designed to do. It is likely a sensor looking at those numbers.


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## MRO1791 (Sep 2, 2016)

MP81 said:


> Bump - wife just messaged me saying the 175 mile/Service Emissions System/Read Owner's Manual Now (while driving) just popped back up.
> 
> I imagine it'll be the same codes.
> 
> Thoughts? The NOx2 reading looks absurdly high - shouldn't it be lower? Could be causing it?


Looking up the fault codes. P11DC is out of range for NOx sensor 2, and P20EE is saying the SCR is not within efficiency limits. The bad sensor is likely causing both codes.


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## MRO1791 (Sep 2, 2016)

Oh, and P229E is the circuit for NOx sensor 2.. all indications are NOx sensor #2. 

B2AAA is likely an issue with your scan tool that has caused or the protocol used for the communication between your scanner and the car.


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## MP81 (Jul 20, 2015)

Yeah, I think I read that about the B2AAA - using Torque Pro and a bluetooth OBDII scanner, so may be one of those. Sometimes it is there, sometimes not.

Yeah, we've had the P11DC for a while - normally I don't think that is grounds for a countdown, but looking at the Biscan graph, the NOx2 sensor is like...10 times higher than the NOx1, haha.

The Message/Countdown went away, as my wife was driving, after she stopped somewhere to do one of her errands.

I'm really not feeling like paying - again - for a NOx2 sensor, given I just replaced it last February (and I don't particularly want to replace it, either). But that's when the warranty was 12 months. About two months later they changed it to 24 months...on the same part number...


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## MP81 (Jul 20, 2015)

It's been popping up and going away somewhat frequently now (it had popped up just before we got to the hotel on Saturday and dropped the car off at the valet for parking - it was gone by the time we got the car back the next morning), so my wife was asking about just replacing it.

Figured I'd go through Rock Auto's site first to see, and it let me process the warranty replacement - should have a new sensor here on Thursday.


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## MP81 (Jul 20, 2015)

My wife said it came back on briefly this morning...but had "reset" itself...to 171 miles. Not 175. This is so, so odd.


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## MP81 (Jul 20, 2015)

Replaced the sensor today - only took me about an hour this time instead of three days like last time, haha.

Started the car (coldish start), and both NOx 1 and NOx 2 were reading the same - hoping we should be good here.


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## MP81 (Jul 20, 2015)

Worth mentioning - that sensor lasted for 27,893 miles (well, less if we count when it started throwing the P11DC code - months back now).


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## BDCCruze (Jul 12, 2017)

@MP81 

What part #?


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## MP81 (Jul 20, 2015)

BDCCruze said:


> @MP81
> 
> What part #?


Sorry, missed your post back then - which part number were you asking about?


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## BDCCruze (Jul 12, 2017)

MP81 said:


> Sorry, missed your post back then - which part number were you asking about?


For the sensor you replaced you talked about in this thread to fix the error code.


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## MP81 (Jul 20, 2015)

Oh, so the NOx2 sensor. AC Delco Part # 12662659 - same part number as the one that I had put in a year and a half earlier.


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## BDCCruze (Jul 12, 2017)

MP81 said:


> Oh, so the NOx2 sensor. AC Delco Part # 12662659 - same part number as the one that I had put in a year and a half earlier.


Oh wow, huh. I recall the square piece bolting on to the side of the air filter box and I wasn't sure what it was. Glad I know now. Thanks!


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