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How to clear DEF light after sensor replacement?

14K views 43 replies 10 participants last post by  hand foot maneuver 
#1 ·
So I got the “def quality poor” message with the mileage countdown to limp mode, no CELs to be read, none on dash, none stored per obd2 scanner.
Ive replaced pos 2, pos 1 should show up any day now.

Which is the best way to clear the light if there are no cels showing?
Gm drive cycle? Better to do it with the obd scanner?
been following the older def threads but no activity.
Any info appreciated, thanks!
 
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#2 ·
Also looking for recommendations on a scan tool, not sure which one to get for the duramax
 
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#3 ·
I can't help with clearing the DEF counter, but I have the BlueDriver OBD-II dongle and software and it's been able to read and clear codes in basically all the modules in all of our vehicles. I originally bought it to deal with a 4WD control module problem with a Jeep my daughter used to have but it's worked great for everything else as well.
 
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#4 ·
Cool thanks drax, ill be looking into that one shortly.
Im getting a little discouraged since it seems most folks get a cel with the def warning and i havent...hmmm
 
#5 ·
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#7 ·
Yup, that's the one!

I'm using this one at the recommendation of someone else here. I bought it specifically because it had the ability to turn on the A/C after-blow feature using software that was written by the person who recommended it. I used it for that and the included software for just looking at things and for that it works great. I have not had to clear any codes (yet?) so can't comment on that part:

What software are you using to enable features like after-blow? Torque + BiScan or something else?
 
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#6 ·
I'm using this one at the recommendation of someone else here. I bought it specifically because it had the ability to turn on the A/C after-blow feature using software that was written by the person who recommended it. I used it for that and the included software for just looking at things and for that it works great. I have not had to clear any codes (yet?) so can't comment on that part:

 
#8 ·
Nice, thanks fellas. Gonna pick up one of those two shortly.
looking into recall
  • N192273630 and see if thats playing in. Weirdest part is theres no cel to read
 
#10 ·
Wow, so just finished at local shop, he has gm tech connect and it showed nothing out of place. Def warning light on and poor def quality msg on dic, still no cels. We were both dumbfounded how there is no record of anything out of place anywhere. Replaced pos2, pos 1 shows up friday, fingers crossed for that but now limited to 4mph, so doing the drive cycle is out. Likely have to get the obd tool to clear it that way. Totals up on about 600 sillybucks all in, maybe more if clearing is difficult.
Ironically was trying to get it in to the dealer for the related recall before this started. Now im afraid theyll charge me even if the recall fix takes care of it.
What a PiTA!
 
#11 ·
Wow, so just finished at local shop, he has gm tech connect and it showed nothing out of place. Def warning light on and poor def quality msg on dic, still no cels. We were both dumbfounded how there is no record of anything out of place anywhere. Replaced pos2, pos 1 shows up friday, fingers crossed for that but now limited to 4mph, so doing the drive cycle is out. Likely have to get the obd tool to clear it that way. Totals up on about 600 sillybucks all in, maybe more if clearing is difficult.
Ironically was trying to get it in to the dealer for the related recall before this started. Now im afraid theyll charge me even if the recall fix takes care of it.
What a PiTA!
Viewing the tests can be done in GDS2.
But it’s not something the service manual has you do. Probably cause it’s a massive headache. But that’s where you see the codes which have not ‘passed’. Basically meaning the code diagnostic has not ran. It’s kind of in a limbo state.

Regardless replacing NOx sensors is a go to first step. You’re only paying like 200 to 300 in labor so kinda meh. And I would imagine they would run a quality test after getting the sensors. Hopefully that’s included in the charge.
 
#12 ·
Gds2 can be done with an obd2 scanner? New to this end of things since the colo has been the only vehicle to give me any troubles like this.
Doing the NOx sensors myself, super easy. This is going to make me get a scanner iguess. About time i had one anyhow i reckon. Pos 1 sensor on friday, can have scanner here by then im sure. Sure would like to go camp this weekend and not dicker with the truck.
 
#13 ·
So, update, got pos 1 sensor in, dash behaving as before, speed limiting wont let me do the drive cycle to try to clear this def light, warning, and speed limiting.
Have the battery unhooked for half an hour to see if that does anything. Prob wont.
How the heck do you get this thing cleared?? Obd2 scanner should be here tmrw.
 
#14 ·
I had a NOx sensor go out and had the dealer replace it. After the swap and clearing the codes, they had to run a manual regen. Part of the procedure, I was told. Hopefully, whatever OBD scanner you get will allow you to do that yourself if needed in the future.
 
#15 ·
Thats what im hoping too. Sounds like you force a regen, then you can clear the light. Cmon amazon, bring that thing
 
#16 ·
Hmm, i need to run thru the rest of the manual, but it seems that i may indeed have bad sheeps pee in there. Bluedriver is pretty easy to use so far. Listing ‘incorrect reagent’

NOx pos 1 running at mid 80’s
NOx pos 2 running at mid 80’s
 
#17 ·
Update for those following.
procured a siphon pump and clean new tubing, hand pumped the def tank empty, spent a lot of time getting every drop i could. Filled with fresh def, or one 2.5 gal at least. Up to operating temp and still no changes. Had to drop the spare and undo thefiller tube to get pump tubing in there.
will be having another session with bluedriver once the hot part of the day is done.
If no luck, its gonna be time for a tow to the dealer.
Good times, we got em.
 
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#18 ·
I am tapping out. Getting it towed to La Quinta Chevolds dealer today. I fought long and hard i say.
 
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#21 ·
Will do. This seems quite unnecessarily mysterious. Pretty weak that a simple emissions issue will disable the truck like this. Tried to make the title searchable.
 
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#24 ·
Will do. This seems quite unnecessarily mysterious. Pretty weak that a simple emissions issue will disable the truck like this. Tried to make the title searchable.
This whole regen thing is the only hangup I have on going to a diesel. With my luck, I'd be in the middle of a family vacation and 200 miles from anywhere and the 100 mile warning would show itself. Why did it have to be so few of miles? At least give the consumer a thousand miles before hard shutdown. That way folks aren't in a bind during the most inopportune time this will occur.
Exactly. Thankfully I haven’t had any issues in 21k miles and traveling, but it could sure ruin a vacation in a hurry.

On the military version of this truck they have what is referred to as a ‘combat mode’ (not that the engine has any emissions on it), but that mode enables them to get out of harms way.
GM should at least provide a means to have a certified ‘OnStar’ rep on ’speed dial’ with the button on the mirror to bypass that nonsense and give the driver the ability to get home or somewhere safe.
 
#22 ·
Fingers crossed that it just wants a computer reset that only they can do.

Ive been balls deep in this thing, flipping over all the stones. Frustrating as hell.
Still not too bad, as ive not had any proper repairs in 138k, only maintenance and wearout parts. Been able to do everything except trans fluid exchange myself.
 
#23 ·
I know the $1k plus diagnostic tools will have the function to force a stationary regen, but not everyone has those funds to throw at a tool.

This whole regen thing is the only hangup I have on going to a diesel. With my luck, I'd be in the middle of a family vacation and 200 miles from anywhere and the 100 mile warning would show itself. Why did it have to be so few of miles? At least give the consumer a thousand miles before hard shutdown. That way folks aren't in a bind during the most inopportune time this will occur.

Friend of mine recently bought one of the 3.0 duramax's in a sierra. He actually bought the one I was trying to strike a deal on. In the first 5k miles he has been towed twice for forced regen related issues. Both times was in a situation where there wasn't a loaner truck available to tow his business related trailer(lawn business) and he couldn't get an appointment quick enough with a dealer service shop to avoid going into reduced power/speed mode. Both times they forced a stationary regen and everything was good for several fillups. He is considering buying a tool to avoid being in this position again since his drive cycles don't seem to fit what are required for the automatic regen process to always complete.
 
#27 ·
It does give a lot more than 100 mi, but sadly i was 180mi from home. I think in all it took just over 200mi to get down to limp mode. I spent all my miles getting parts and getting to a shop to try to fix it.
 
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#25 ·
So I got the “def quality poor” message with the mileage countdown to limp mode, no CELs to be read, none on dash, none stored per obd2 scanner.
Ive replaced pos 2, pos 1 should show up any day now.

Which is the best way to clear the light if there are no cels showing?
Gm drive cycle? Better to do it with the obd scanner?
been following the older def threads but no activity.
Any info appreciated, thanks!
I have the Bluedriver scan tool. Lifetime support. Interactive with what others have done to fix problems. Best $99 I spent. Some faults won't clear with a scanner. You need to drive the vehicle and depending on its setup it either looks at cycles driven or time/miles driven. I had an intermittent one time EGR fault on my Chevy cruze diesel. Fault was locked. After driving a few days it cleared itself. Basically it looks at the system and if it doesn't fault again it clears. The CEL you can clear anytime. Hope that helps.
Bluedriver on amazon. Best deal.
 
#28 ·
I have the Bluedriver scan tool. Lifetime support. Interactive with what others have done to fix problems. Best $99 I spent. Some faults won't clear with a scanner. You need to drive the vehicle and depending on its setup it either looks at cycles driven or time/miles driven. I had an intermittent one time EGR fault on my Chevy cruze diesel. Fault was locked. After driving a few days it cleared itself. Basically it looks at the system and if it doesn't fault again it clears. The CEL you can clear anytime. Hope that helps.
Bluedriver on amazon. Best deal.
i have that too. It doesnt have the ability to clear the def light though. It does clear cel but i have no cel thrown.
 
#30 ·
GM drive cycle is surprisingly hard to do in traffic with like, other people driving. I only had one shot at it before limp mode and it didnt go to plan due to other traffic.
 
#31 ·
Just spoke with svc guy, theres a shred of hope that this could get cleared up by the open recall related to the SCR. Fingers crossed for that. Theyre backed up, might be a few days before it gets attention though. Hes pretty confident it will, but otherwise confident its just a computer reset and force regen that only they can do, or that i cant w my obd2 scanner. Hoping the worst case is paying for an hour of labor to make computer hand magic on it.
 
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#32 ·
Truck is done! Exactly what i thought, just needed a reset of the reductant system from their magical gm cpu. The recall thing was done, but didnt fix the problem, so i had to pay for one hour labor. Im just glad its done and i wasnt losing my damn mind. On way to pick it up now before my she has to go to work.
 
#33 ·
Hey sorry I’ve been busy this past week. But I try to help out everyone’s diesel issues.

The reset they did is called a DEF FLUID QUALITY TEST. Which is not too unsimilar from a service Regen. Basically just runs the vehicle.

I made an app called Gretio Gretio - Automotive Scan Tool - Apps on Google Play
Which when combined with an OBDLINK MX+ allows people to do them at home for about $150. Bypassing the expensive dealership or expensive scan tools generally required.

There are also other resets but the quality test is the go to. Ie you can reset the NOx sensors but that won’t really accomplish much.

Anyway happy the truck is fixed. If it comes back, now you know.
 
#34 ·
Cool, thanks for that. Certainly not impossible for it to happen again.
They said it was stuck in “level 7 limp mode”, they unstuck it from that, and did the regen recall also. Business as usual again. Thankfully only one labor hour at $175, and they made sure to mess up my tire pressures for me free of charge🤡 i run e rateds and carry a pop up camper so i run them at 41. No bigs but ironic. Level 7 limp mode sounds like it needed a viagra or something. Didnt know there were levels of limp mode. Didnt really pin down the cause, but hopefully wont give me any more trouble and my sensors are new now.
What a snafu!
 
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#36 ·
So guess what. Drove 270 mi from home and the damn thing went into limp mode again. No 65mph, no 55 mph, just straight to 4mph. Same “def quality poor” msg on the dic, no cel. Gotta get towed home to the dealer and rent a car since no ride alongs with covid. Only rental car available is a convertible mustang, get to drive home like a european tourist!

This is getting ridiculous. Its been fine for a thousand miles since the last reboot of the computer and im hoping thats all it is this time, but the jump directly to limp mode has me worried.

I just drove it like 600 miles over this past weekend, palm springs to big pine CA and back, then had to come back up again to reno for a work stint. Didnt make work obviously.

This past weekends trip was up to 9500’, fully laden, carrying my camper and with my lady. Not a single issue. Hit home and found out i had to come back up to reno/tahoe for some work. Made it as far as bishop Ca and got shut down.

Local diesel shop booked out for over a week, nearest dealer 170mi further north, so i chose to use my 200 mi free tow to get it home, paying for the remaining 70mi.
 
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