2021 Silverado Duramax 3.0L DEF Sensor Issue

[Ross McKenrick]

I have a new 2021 Silverado (<5000mi) with a 3.0L Duramax diesel engine. I just completed a 4000 mile cross-country trip from Oregon to Massachusetts towing a 3600lb RV trailer and it quickly became apparent that I have a problem with the DEF system. When it is not towing, the truck is getting 25+ mpg, but I averaged approximately 10 mpg during this trip so I consumed about 400 gallons of diesel fuel. I am told that the DEF consumption should be in the range of 1-2% of the fuel consumption. Using this calculation, I should have consumed about 4-6 gallons of DEF. In actuality, I consumed 6 bottles (15 gallons) of DEF. I'm surprised that I didn't get better fuel and DEF consumption, but the most immediate problem is what appears to be faulty DEF sensors in the tank. Each time I filled the DEF tank, the DEF gauge would show full (8/8). After some number of miles (125?), the gauge would drop to 7/8, and then (after 250 miles) it would drop to empty. The info display would then flash "DEF Empty Refill Now" alternating with "500* mi Until 65 MPH Max Speed". *The 500 would count down until I stopped the truck and refilled the DEF -- which I would do within 5 miles. However, the DEF tank would overflow after pouring in about 2 gallons (from the 2.5 gallon bottle), spilling down the side of the truck, onto our shoes and leaving a puddle wherever we were.

 

There may be a problem with our overall fuel and DEF consumption under tow--but I could live with that if the DEF sensors were working correctly and showed empty when the tank was actually empty and not 60% full.

 

The truck is at the dealer now, but the dealer is having trouble pinpointing the problem. Is anyone else experiencing a similar problem with the DEF sensors / DEF gauge?

 

[Forrest Friedrich]

My '21 Sierra 3.0, which is at 10k miles, gave me a message yesterday saying that the DEF tank was empty, and that I had 500 miles to fill it. But I knew that it was about 60% full. The message seemed to be elevation related, and went away when I got close to sea level.  If I put a scanner on the OBD port the DEF level reads 60%, then 0 for several seconds, then 60%, then zero for several seconds. Gauge in the dash always reads correctly, unless it's telling me to refill immediately.

 

Not looking forward to calling the dealer. Pretty sure I'll hear, "Gee, we've never heard of this problem before. Without a Check Engine Light there's not much we can do." 

[A Chin]

I've experienced similar issue when towing 7200 lbs. Gauge reads 60% and then after 30km or so, it's showing def tank empty and about to go on low power mode. Mentioned to the dealer and they said "def fluid gauge is not a float style gauge and it could take a few ignition cycles to get an accurate reading and also if the level is just above or below a certain calibrated spec, it may give false readings".  It looks like its on bulletin 20-NA-082.

[honda65]

I had a problem with mine as well. I have a 21 1500 LTZ and I went to fill my DEF because the gauge said I was about 2/3rd down. Normally at this mark i can put an entire jugs worth of DEF (2, 2 1/2 gal?) with room to spare. But this time it over filled. Didnt seem to cause any issues but it did throw the check engine light. I just started a long trip so i jist kept driving and hoped for the best. As the DEF dropped the light finally went off.

But the other day, after topping it off at the DEF pump it flashed "DEF almost empty, have 1000 left" or something to rhat extent. But the gauge itself showed full. The warning went off a couple more times but has stopped.

Im glad I saw this because im aitting at rhe dealer getting my 15000 service so I think I will mention this to them

[Randy640]

On 8/4/2021 at 12:59 PM, Ross McKenrick said:

I have a new 2021 Silverado (<5000mi) with a 3.0L Duramax diesel engine. I just completed a 4000 mile cross-country trip from Oregon to Massachusetts towing a 3600lb RV trailer and it quickly became apparent that I have a problem with the DEF system. When it is not towing, the truck is getting 25+ mpg, but I averaged approximately 10 mpg during this trip so I consumed about 400 gallons of diesel fuel. I am told that the DEF consumption should be in the range of 1-2% of the fuel consumption. Using this calculation, I should have consumed about 4-6 gallons of DEF. In actuality, I consumed 6 bottles (15 gallons) of DEF. I'm surprised that I didn't get better fuel and DEF consumption, but the most immediate problem is what appears to be faulty DEF sensors in the tank. Each time I filled the DEF tank, the DEF gauge would show full (8/8). After some number of miles (125?), the gauge would drop to 7/8, and then (after 250 miles) it would drop to empty. The info display would then flash "DEF Empty Refill Now" alternating with "500* mi Until 65 MPH Max Speed". *The 500 would count down until I stopped the truck and refilled the DEF -- which I would do within 5 miles. However, the DEF tank would overflow after pouring in about 2 gallons (from the 2.5 gallon bottle), spilling down the side of the truck, onto our shoes and leaving a puddle wherever we were.

 

There may be a problem with our overall fuel and DEF consumption under tow--but I could live with that if the DEF sensors were working correctly and showed empty when the tank was actually empty and not 60% full.

 

The truck is at the dealer now, but the dealer is having trouble pinpointing the problem. Is anyone else experiencing a similar problem with the DEF sensors / DEF gauge?

 

Yes I have a 2020 GMC 3.0 with 30K miles just completed a 2000 mile trip from Texas to Phoenix Arizona. I used 8 2.5 containers of DEF. The gauge showed the tank empty but was full. A engine light came on so I pulled into Royal GMC in Tucson.  Nice friendly people.. They cleared the code and reset the DEF system so I was on my way. 400 miles down the road the DEF light came on again so I pulled over to more DEF in the tank and again it was full but the gauge showed empty. I was pulling a 14 foot flat bed trailer with a golf cart on it. The dealership did not have the part to repair the truck. When I got back home and took it back to the dealership and gave them the paperwork provided by Royal GMC they said without a code they could not help me. Still as this date the DEF gauge now shows full but pops up on the dash saying I only have 252 miles to empty.  This is the 3rd of 4th time this truck has been in some GM shop for the same problem.  Just wondering if there is a fix..

[Steve-2019]

If this were my truck, I would run it until it gave me the message of ****** amount miles until speed limited (limp mode) then take it to my dealer.

Edited November 17, 2021 by Steve-2019

[redwngr]

Last 2 full size LED segments are supposed to be about 1 gallon each.

The others are supposed to be about 1/2 gallons each.

 

Seems like the top one depends on how much it gets topped up after 'full'.

 

3.0 tank only holds 5.3 gallons.

When 3 full size segments are on, the manual thinks that it will take 2.5 gallon  -- so with only 3 on it's still about 1/2 full.

 

 

 

 

 

Edited November 19, 2021 by redwngr

[Truckcamper nomad]

I am on a trip now with my 2021 6.6L Duramax. Got the warning that my def was nearly empty although I had filled it about 300 miles earlier. I added about 1 gal and ran it over. I then watched my DIC gauge and it bounced from nearly empty to nearly full and everywhere in between over then next few hundred miles. We are at the beginning of a 3000+ mile trip so I can’t run to my dealer! I will call a dealer in Moab on our route tomorrow and see if there is a quick fix. Hope I don’t get put in limp mode! Any advice out there?

[AngryBeaver]

On 12/19/2021 at 6:53 PM, Truckcamper nomad said:

I am on a trip now with my 2021 6.6L Duramax. Got the warning that my def was nearly empty although I had filled it about 300 miles earlier. I added about 1 gal and ran it over. I then watched my DIC gauge and it bounced from nearly empty to nearly full and everywhere in between over then next few hundred miles. We are at the beginning of a 3000+ mile trip so I can’t run to my dealer! I will call a dealer in Moab on our route tomorrow and see if there is a quick fix. Hope I don’t get put in limp mode! Any advice out there?

This happened to me yesterday. I had just gotten a low DEF warning so I was going to fill it, but the tank only took about half a box. Between 1 and 1.5 gallons. Checked the gauge and it was full. I drove it for another 100 miles and got the 500 mile warning again, except this time it went from 500, to 300, to 100, to 60, to 10, to limp mode in about 30 feet. Took it straight to the dealer and of course, they turn it back on and it says 100% full.

 

It's at the dealer now but like with the "crank no start issue", they've never heard about this and I'm sure they're going to find nothing wrong.

[Treefarl]

I have a 2020 Silverado 1500 Diesel Denali w around 9,000 miles. I recently filled the DEF and the sensor read “Poor DEF Quality” 70 miles to 55 mph Max. I used new DEF I bought on Amazon. Brought to Dealer, they say it’s probably a bad sensor, and it’s on back order for 1 month plus! So I’m out of Lease Payments + I have to rent a comparable truck for $5k a month. Is GMC doing anything for their customers on this? Basically a $90,000 truck that can’t move due to a faulty sensor. This is totally unfair, was about to get the wife the Yukon XL but this is making me boycott GMC (and telling everyone I know) for life. Any help out there is much appreciated. 

[Motor4150]

I have a 2021 1500 Duramax with the same issue. The dealer and factory brushed it off saying they didn't see a code. Very frustrating!

[Andrew Mc]

I am having the same issue as everyone else here. 2021 Silverado with 3.0L Duramax, towed a 4500 lb trailer a total of 650 miles and used almost 8 gallons of DEF.  Took the truck to 2 different Chevy dealers and both said the system is working properly.  Despite also stating the system should only use 1% - 2% DEF per gallon of diesel.  I used about 50 gallons of diesel on the trip which should only be a gallon of DEF On the high end of Chevy’s own estimate. Hell even if I doubled their estimates it should have only been 2 gallons used not 8… Neither dealership could explain to me how the math was so far off. 
 

Not sure what the point of having a diesel truck is, if I can’t tow with it…

[Alice Sabatini]

We had the exact same issue in our 2021 GMC Sierra Duramax with 20k miles, pulling our 4600 lb trailer from NC to ND. We kept getting DEF warnings when the tank was nearly full. Put in only a gallon (all it would hold) and sensor would reset for short while then warning would come on again. Next day, seemed ok, no warnings. Next day, got check engine light as soon as we started out. Using Onstar, diagnosed emissions problem P249C. Turned out was DEF injector failure. We had to find dealer that had the part and wait 5 days to get part installed because of holiday weekend. No problem since install it we aren’t home yet. Part replacement was covered by warranty. 

[NEHP]

Same issue with 2 different tanks on my 2021 Chevy 3.0.  Original issue started March of 21.  Brought it into the dealer and they said they'll order a new tank but unfortunately was a 3 month lead time.  Luckily I never got speed limiting prompt, only the level on the display clearly wasn't reading correctly with how much fluid i had in the tank.  Got the new tank replaced in the middle of June, 3 days later and with a full DEF tank i got a speed limiting message that would take effect in 140 miles or so.  Brought it into the dealer and said I don't want it back until you fix this.  They've had it since then and it's the middle of July.  They have another tank on order (Rev 2 is what they call it, apparently GM redesigned the tank) but the part is on backorder so dont know when it'll get in.  Chev dealer said they're seeing this in 3/4 tons a lot too, said they got one in the other day where the speed was reduced to 5 mph, could barely get it up the ramp to work on it.  Chev dealer said they have they have no way to bypass the issue via software, guessing that's intentional to comply with gov regulations. I understand the concept and value behind this but imagine if this happened to you in the middle of winter somewhere in podunk BFE.  SOL.  All in the name of emissions.

 

Calling the dealer about every 3 days to get the latest, luckily I was able to snag a Equinox loaner from them but that was like pulling teeth especially given the current inventory situation.  Good luck all.

[NEHP]

Update, dealer called me on Wednesday and said they have a new tank in and were able to install it that day.  Installed it on the 21st in the afternoon and i picked it up in the evening before they closed.  No issues yet.  Took about a month to get the second version of the tank