# Weird things happening. Does anyone know if the AC system is somehow connected to the DEF system?



## TGillis (Aug 25, 2017)

Hey! So I have on and off been getting the count down to 104km/hr because of the "service diesel exhaust fluid system"
The interesting thing is, is I have discovered it comes on when I use my ac for more than 5 minutes. 
How does this make sense? 
Also, can the count down time be cleared without going to the dealer?
Thanks so much in advance!!


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## Snipesy (Dec 7, 2015)

TGillis said:


> Hey! So I have on and off been getting the count down to 104km/hr because of the "service diesel exhaust fluid system"
> The interesting thing is, is I have discovered it comes on when I use my ac for more than 5 minutes.
> How does this make sense?
> Also, can the count down time be cleared without going to the dealer?
> Thanks so much in advance!!


No relationship besides the engine having to work slightly harder.

As for clearing it... You don’t. Not even the dealer can. You need to run tests and IF those tests pass, then the code clears.

As for running those tests at home. You have the app I and a few others here made. And that’s it... You can find a used snap on tool which might do it for like $2000? GMs setup is like $1000 plus $1300 ish a year... Which is actually pretty reasonable.


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## TGillis (Aug 25, 2017)

Snipesy said:


> No relationship besides the engine having to work slightly harder.
> 
> As for clearing it... You don’t. Not even the dealer can. You need to run tests and IF those tests pass, then the code clears.
> 
> As for running those tests at home. You have the app I and a few others here made. And that’s it... You can find a used snap on tool which might do it for like $2000? GMs setup is like $1000 plus $1300 ish a year... Which is actually pretty reasonable.


Thanks for the reply. 
So the wiring to the ac and def pump are not interconnected? I am wondering if my ac is getting bad and causing more pull on more cutting it from the def pump.

You say you don't clear the service diesel exhaust fluid system warning count down? 

Ok, I am getting mixed information regarding that one. 

Why is that I would buy a snap on tool? I am not sure why you are saying that.

Thanks!
Tracey


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## Snipesy (Dec 7, 2015)

TGillis said:


> You say you don't clear the service diesel exhaust fluid system warning count down?
> 
> Ok, I am getting mixed information regarding that one.
> 
> ...


There is no button which says “Reset SCR Warning”. It’s not that simple otherwise the dealership techs would try and bypass the system. Simply put, the vehicle has to clear it on its own after you fix the problem.


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## Renwo (Jan 29, 2014)

I had a bad sensor and was able to "clear" the count down to death using the check DEF quality test on Snipesy's app "Gretio" which passed gave me enough time to fix the root cause.


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## boraz (Aug 29, 2013)

TGillis said:


> Thanks for the reply.
> So the wiring to the ac and def pump are not interconnected? I am wondering if my ac is getting bad and causing more pull on more cutting it from the def pump.
> 
> You say you don't clear the service diesel exhaust fluid system warning count down?
> ...


its mandated by the govt to not be able to clear the code

has to be fixed for the code to go away


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## snowwy66 (Nov 5, 2017)

You guys can't have your dpf cleaned?


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## pandrad61 (Jul 8, 2015)

snowwy66 said:


> You guys can't have your dpf cleaned?


Big rigs have removable and easy to service DPF our small diesel do not. On big rig shops they can clean out DPF, if only it where that easy for us.


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## Snipesy (Dec 7, 2015)

snowwy66 said:


> You guys can't have your dpf cleaned?


We’re talking about the SCR.

80% of the time on the Diesel any SCR warning is due to NOx sensor 2 being ‘poisoned’ by DEF seeping through the entire length of the SCR Catalyst.

Sometimes a good Regen will clean the sensor and it’ll work for a long time. Other times not so much and the sensor has to be replaced. Generally depends on the age of the sensor.


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## snowwy66 (Nov 5, 2017)

pandrad61 said:


> Big rigs have removable and easy to service DPF our small diesel do not. On big rig shops they can clean out DPF, if only it where that easy for us.


I drive big rigs. 

Hence,.the question.


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## pandrad61 (Jul 8, 2015)

snowwy66 said:


> I drive big rigs.
> 
> Hence,.the question.


I figured that’s why I responded. On a diesel rig they are vastly more expensive to replace so they came up with designs to allow cleaning and reuse. Our small diesels not so much. I wish they had to be honest so it can be cleaned and resumed as needed.


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## snowwy66 (Nov 5, 2017)

They're not that expensive now.

They get cleaned. The next time it's replaced. I beleive is the maintenance.

Problem is finding someone with a cleaner.
Salt Lake dealer had one. Vegas dealer didn't. At that time. Vegas was twice the cost, too. Because they had to send it out.


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## Snipesy (Dec 7, 2015)

pandrad61 said:


> I figured that’s why I responded. On a diesel rig they are vastly more expensive to replace so they came up with designs to allow cleaning and reuse. Our small diesels not so much. I wish they had to be honest so it can be cleaned and resumed as needed.


It’s actually more so for DPF retrofit kits. Which need periodic cleaning. Hence why the cleaning services are almost exclusively in California.

Now many OEMs do have cleaning in their maintenance schedule. And by cleaning I mean core charge swap with the OEM for a expensive ‘remanufactured dpf’.


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## pandrad61 (Jul 8, 2015)

Snipesy said:


> It’s actually more so for DPF retrofit kits. Which need periodic cleaning. Hence why the cleaning services are almost exclusively in California.
> 
> Now many OEMs do have cleaning in their maintenance schedule. And by cleaning I mean core charge swap with the OEM for a expensive ‘remanufactured dpf’.


I’ve seen a few stop shops that will bake them for X time then air blow the remainder out. I figured this was for when regens don’t cut it anymore. Sucks it’s not a lifetime clean and re run but rather once or twice then core in. If diesel has these so should gasoline. Why do gas cars get to have clogged or and cats and no countdown to slowdown but we do.


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## TGillis (Aug 25, 2017)

Thanks for the replies. I initially had the Nox position 2 sensor warning code, now this service exhaust fluid emissions. I asked about the electrical connection because I got the warning and the count down timer, after a restart it didn't come back on for a couple days. I couldn't remember if I used the ac that day. The count down timer continued to count down over the 2 days of driving but then I didn't have it again for a couple days. Then I turned on my ac, I had it on for about 5 minutes and just as I was about to turn my ac off the warning light came back on but then turned off as soon as I turned my ac off. I didn't use my ac for a few days, no warning. Then it came back on a couple days ago and the countdown had reset, back to 160 before the 104km/hrs.
Does anyone have the breakdown of this system? I looked at buying the manual, I see it is $400.
Or does anyone know how the system operates? Should the pump run the whole time the car is running? I have everything removed out of my trunk the whole system is exposed, I have the seats down. When I start the car you can hear the pump, you hear fluid circulating then the pump shuts off, as I am driving or idling, I will hear a click every now and then but the sound of the pump is not operating like at start up. When I turn the car off the pump engages and runs again, I assume taking the fluid out of the lines and returning to tank.
I did hook it up to a code reader and I got the codes P20B9 reductant heater 1 control circuit, P21DD
It is 35 degrees here, why would the heater be needed?
Anyhow if anyone has the system break down or how the system operates I would really appreciate it. I see there is a few different electrical connectors and modules.
I have looked online for hours and can not find anything.
Thanks in advance!


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## ChevyGuy (Dec 13, 2014)

TGillis said:


> I looked at buying the manual, I see it is $400.


Look into getting a subscription to Alldata. $30 for a year. $50 for five. And I've seen hints that it's more up to date then the Helm manual.


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## TGillis (Aug 25, 2017)

Took the car to the dealer because the codes that were coming up reminded me of the recall work I had done in 2017. I had gone on my GM OnStar account and it showed special warranty up to 193,000km or 10 years, I am at 183,000!!!
I took it in and sure enough, the exact same issue from before. I know there is a thread on here somewhere about it.
Round 2 for me!


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