I hope you can get a real answer from a GM tech or someone really in the know. Personally, I am trying to track down how the ECM/BCM determines the DEF level and have come up with nothing on the posts I have placed. Considering I have no access to GM technical documents or manual I too am hoping we can get the answer here.

 

That is a sensor of some sort but i am not able to see the part number on my look up site. Says to contact dealer.

 

The reductant quality sensor includes an integrated temperature sensor to measure reductant fluid temperature. The reductant quality sensor is located in the reductant tank and uses an ultrasonic signal to measure reductant fluid quality. The reductant quality sensor communicates with the reductant control module using serial data.

 

Is the level sensor part of the reductant quality sensor?

 

No, it's part of the pump/ heater module..It has a little float in it.

 

No, it's part of the pump/ heater module..It has a little float in it. View attachment 1102283

So in theory if it's just a float, then with the info system glitching between "OK" level and "--" level it should be an issue with the wiring/plugs or the control module(sending/recieving module)?

 

Ouch, looking at the pictures even if we could get to the actual leads of the float it might be possible to use a relay to open the circuit and place a resistor to simulate a full or almost full def tank. This would release the Information center from being locked displaying the low def and reduced speed warning.

Perhaps someone who has access to one of these tanks or a vendor can figure it out. What a great opportunity for an aftermarket add on product.

 

More than likely it's a connector issue. Inspect it and look for any pin corrosion.

 

I inspected and reseated my plugs when I took the pic and didn't see any damage or corrosion. The design is poor for living on a gravel rd, the skid plate has about a 1 inch gap between itself and the electronics on the bottom of the def tank. That was packed with dirt and debris (never thought to take it off the 3 years I've had the truck). So far that's been almost 2 days ago and the check engine light went out and my level has been staying steady at "OK". The day I posted I watched the level cut to "--" at least 3 times for approximately 5 mins each time. I will update if it does it again, the bright side is it looks like I can change it myself without dropping the tank if need be (and if I can get the part). Anyone know, if it comes to changing things, if I need to bring to dealership to program after change out?

 

Do you have any photos of the plugs you inspected and reseated? Did just cleaning the plugs and stuff fix your problem? I am having the same issues you did and trying to figure it all out. I am not a mechanic by even a stretch of the imagination so I am struggling. I am 525 miles from my destination and I am supposed to be at work in the morning and not a lot time or funds. I have a 2019 Durmax 3500 got a low def message and before I made it to the next exit it started running rough, check engine light came on and service emission now message. I stopped at the next exit, put 5 gal of Def in and no change. Went to the nearest O’Rielly’s and they cleared the code and messages came right back on. Their diagnostic thing said several different things about the def sensors and said my #6 injector was sticking. I would appreciate any suggestions.

 

By the way, if anyone is curious, it's four 10mm bolts to remove the plastic and another two 10mm bolts, two 10mm nuts, and three 13mm bolts to remove the skid plate. Takes minimal time to remove it, so may be worth it to take off periodically to clean dirt and debris off your electronics.

 

Has anyone had any luck changing the pump module and fixing the Code P1050

 

Nope. I have the same problem.

 

Hello everyone, my 2018 GMC is not transmitting DEF level with the service engine warning. Originally, receive a P203D code and everything indicated it was the level sensor. I was led to believe that it was part #8 Integrated in the tank. Changed the tank $700 dollars later, no change! Now, I am getting code P1035 which has a similar description. After noting that the float built into the pump, I’m left to change it snd hope for the best.
Hope this helps someone out there!

 

Same fault/problem! New tank/sensor assembly and new level/temp module (Mounted to DEF tank) and still have same problem. A LOT of wires there to pin out. Any ideas??

FYI 2018 and up have a different pump/tank/module.

 

Does anyone have any luck getting this resolved? My truck said it was low on DEF. So when I added more fluid it overflowed. It was ok at first. It is now saying that it is empty and will have a 65mph limit in 180 miles. Will it be ok as long as it has DEF fluid in it? Should I replace the level sensor?

 

You ever figure it out?

 

My 2019 is doing the p1050. Diesel shop says its serviceable but dealer will need to clear the code but the dealer says def tank has to swapped out sending unit is not serviceable. Any new info on this topic?

 

camaroguy692 did you get yours fixed?

Im in the same boat with my 19'. Started out with a low DEF message (288 miles). So I went and put 2.5 gal from a pump in it. Next day (100 miles from home) I got a poor quality DEF message with the threat of reduced power in 65 miles. Went to O'Reillys and had the codes read, no active codes at that time so they reset it (Codes were P0203D and P1050). Ive dropped the cover and skid plate (and 25 lbs of dried mud). about to unplug everything and clean the connectors with contact cleaner. Wish I knew someone with a module I could substitute test it with. Currently the def level reads "- -", but does go to OK briefly when I reset the P1050 code.

 

Some info attached. May/may not help your particular situation

 

If you start with a p1050 it is more than likely the sensor molded into the tank(2018). Some run $425 (GM Parts Direct, North Carolina) and go as high as $700 from dealers. If the sensor does not tell the ecm there is enough def in the tank to use, it pretty much shuts down the whole system. Codes P20cb, p20bb, p20bf will also pop up and if you continue to drive it will start the countdown. Check out O'Rileysautos on youtube, he is in the UK I believe and does not deal with Duramax but shows how to diagnose all issues and repair including flushing the DPF and everything else that can cause DEF/DPF codes. He even gives reviews on Scanners like the Launch 919x and Autel 808s.

 

I just went through this a couple of months ago. 2018 High Country 2500. 165,000 miles.

I was low on DEF and stopped by Autozone. I went in to grab a box of BlueDEF and the guy behind the counter said the Autozone brand was on sale. Almost $10.00 less for the same quantity. As much as I hate paying for DEF I went for it.
I bought 2 boxes and poured it in the truck right in the parking lot.

I drove around for two days with no issues. On the third day I was driving and came up on a roundabout. Right in the middle of the turn I get a warning light. 65mph limit in 165 miles. 1/2 a mile down the road I get to another roundabout.
Half way through it kick the warning again. I usually get around 800 miles a box of DEF so in my mind 2 boxes would have been good for 1600 miles. I've only driven around 150 in 3 days. I pull over in a parking lot and check the information center in the dash. Now it reads "--". I get a box of BlueDEF at O'Reilly Auto Parts and fill the tank. Its still reading "--".
I limped home expecting all hell to break loose but, made it home fine.

Once home I hooked up my scanner and threw a bunch of codes. All related to the DEF system.
After some research I decided to replace the pump. I found this one on Amazon.
amazon.com/Replacement-2017-2020-Silverado-84545446-84162467/dp/B0D5CJG23M
Once it arrived I removed the plastic cover, the skid plate then disconnected the harness and one fluid line from the pump.
Before cracking the retaining ring I placed a bucket under the pump. A couple hard whacks with a punch and the ring was off.
Surprisingly not much fluid came out? I'm guessing when the pump is not functioning correctly this thing must be drinking it? Who knows... My concrete is almost white and any leaks would be immediately visible.

Anyway, I installed the new pump and added new DEF. Before I put the skid plate and cover of I cranked up the truck and checked the information center. All good!! I kept the truck running for 30 min. Checking for leaks. Nothing.
I installed the skid plate then the plastic cover. Drove into town. And topped the DEF.

I decided to throw the scanner back on and cleared the codes. Turned off the truck for 30 min. then restarted it and ran another scan. Everything clear. P1050,P20EE, P249D, and P203C All gone. I ran a scan again 2 weeks ago just out of curiosity everything is still clear. I don't know if this will help anyone or not but, this is what worked for me.
Fingers crossed..

 

After the sending unit was changed did code vanish?

 

Any updates on this? I have a 2018 GMC 3500hd with the L5P. Started getting the P1050 code and a few others. P204c,P204b etc. Replaced the def pump Module. That lasted about a week and started getting the same codes again. I took out the new module and sent it back to Summit. (By the way, stealership wanted 1700.00 to replace. Found the exact same part number on Summit for around 600.00) Replaced the, what i thought was bad, new module with the original. Same exact codes. While waiting for the exchange pump to get here, I was limited to 55mph. Just installed the new pump today, cleaned all the wire connections with electrical cleaner, and filled the tank. Hooked batteries back up, truck started with no engine light. Shut it off, went to start again and the p1050 code popped back up. Cleared the codes again and so far they are staying off. What is everyone finding when this happens? I can't be the only one who's replaced the def pump module several times and got the same results. The dealership i bought the truck from sold me the extended service agreement, but never mentioned that none of them cover anything def/emissions related. So I'm stuck paying out of pocket

 

Long thread; still active? I may as well jump in on this too. Getting the P1050 myself and have noted that occasionally, with a first start up of the day, the DIC shows "OK" for the DEF level. Hit a bump in the road or something it goes "--". I don't believe it's saying the tank is empty as I am NOT getting any messages stating mileage has been restricted. I also have an Autel handheld reader that displays live data and it's telling me that I have at least 70% capacity. I tried topping it off the other day and the filler tube overflowed. So no, it's not empty. When it does get near empty (~20% or so), a message will pop up on the DIC. I haven't gotten that yet. I'm beginning to think it does have something to do with the connectors or possibly what was posted earlier about the crud buildup under the pump. Mine drives fine, it will do a (mobile) regen and the NOx1 & NOx2 sensors are telling me the DEF injection system is doing its job. I"m going to start with the previous recommendation of removing the skid plate and looking for the connectors. I can't see how this intermittent failure is suggesting a restricted mileage condition is imminent, at least not at this moment. (BTW: 2017 with 177K on her).

 

@Citori1 did you have any luck? I am having the same issues on my 2017. Had code P1050, replaced the pump/sensor, now the gauge will sometime show 27%, but mostly shows "---" with CEL still on. My Edge CTS3 is saying numbers but continuously changing.

 

@Citori1 bump again, did you figure this out? I have the exact same behavior on a 2017 with 95k, right down to the reader showing 70% (even after I overfilled the tank.) I also measured the resistance of connector pins 15-16 and 16-17 according to diagnostic procedure and they are in range. The behavior seen here seems unlikely to be caused by a control module in my mind. No limp mode or warnings yet, but I have two camping trips within the month so I am hoping to get this resolved before that point.

 

https://www.coloradofans.com/threads/p1050-reductant-sensor-malfunction.431588/