# Another low quality DEF message



## gunner6165 (Dec 28, 2014)

A bit of back story, check engine light for DEF heater came on before Thanksgiving, didn't get in to the dealer until after Christmas. Paperwork says 'Emission reduction fluid tank reservoir' was replaced.
Picked up car new years eve. Dealer is 1 mile from my house. Car sat until I drove it to work yesterday. Driving to work this morning low quality DEF message came on. My normal commute is 70 miles round trip, 90% highway.
Read on the forum about others with this problem, and decided to watch NOX 1 & 2 sensors on commute home. 
So, at start, NOX 1 was 199, NOX 2 was 299. Sat and let car warm up a minute, then as I drove through parking lot, NOX 1 would go up & down with throttle, but NOX 2 did not move. About 5 minutes into the drive did the NOX 2 sensor move, it jumped to about 3500, dropped to about 100, jumped again, then settled to about 200 at idle. NOX 1 was similar value at idle. During the rest of the commute, NOX 1 would go up during acceleration, and at steady throttle, both would even out. Upon letting off, NOX 1 would drop first, followed by NOX 2 about a second later.
I did notice a few times where NOX 2 readings would jump up to between 2500 & 3500 for no apparent reason. It would just as fast drop to about 200. NOX 1 never did this. Once was with cruise on at 70, another was at idle at home. 

So, I'm thinking my NOX 2 sensor is starting to go out, and it may be coincidence it happened after my 'Emission reduction fluid tank reservoir' was replaced, but I'm not sure. 
Car has 98000 miles, and has been trouble free except the emission reduction fluid tank reservoir (DEF tank), which has been replaced twice now. I have an appointment for Friday at the dealer. Am I thinking correctly regarding the NOX 2 sensor? I don't want to pay dealer price for the repair if I can avoid it.

Thanks for your help.

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