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My 2021 Duramax with 20K miles randomly gives me the "DEF tank empty" and threatens to reduce my speed. It usually clears itself after a few miles but did go into limp mode once. On that occasion I had the codes cleared and it was fine after a few miles. We are planning a trip to Alaska and don't trust my new truck! I realize many people have gotten this error. My local dealer says I need a new DEF tank, but I have been waiting 3 months and still have no delivery date as it appears this is a common problem and there is a supply issue. I think I understand that this is an issue with the tank heater somehow interfering with the DEF tank gauge sensors. Are others having problems getting a DEF tank, or have others found a work-around for this (besides doing a delete which I am not going to do on a new truck!)?
 

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I have a 2021 with 23k on it, hasn’t been an issue for me. I’ve had the standard warnings as the level reduced even taking it to where I was going to be limited.

Now I did have a similar issue that was cause by a bad def injector, took the dealer a day to get it in. Also had similar esc issues when an egr was starting to fail, took the dealer a week to get that in. First time i had an issue i was 800 miles from home, it would clear it self and never actually limited me.

Good thing about owning a GM product is there are so many dealers you can go to when on the road, i believe you can also get some priority when traveling. Being the dealer can clear it you could also have another do the same as it should show your waiting on repair parts.

I personally wouldn’t worry.
 

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My 2021 Duramax with 20K miles randomly gives me the "DEF tank empty" and threatens to reduce my speed. It usually clears itself after a few miles but did go into limp mode once. On that occasion I had the codes cleared and it was fine after a few miles. We are planning a trip to Alaska and don't trust my new truck! I realize many people have gotten this error. My local dealer says I need a new DEF tank, but I have been waiting 3 months and still have no delivery date as it appears this is a common problem and there is a supply issue. I think I understand that this is an issue with the tank heater somehow interfering with the DEF tank gauge sensors. Are others having problems getting a DEF tank, or have others found a work-around for this (besides doing a delete which I am not going to do on a new truck!)?
I have heard of DEF tanks being on back order for the HD trucks on and off since DEF has been introduced, I don't know if they have been able to increase the regional warehouse stocking? :)
 

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Discussion Starter · #4 ·
I have a 2021 with 23k on it, hasn’t been an issue for me. I’ve had the standard warnings as the level reduced even taking it to where I was going to be limited.

Now I did have a similar issue that was cause by a bad def injector, took the dealer a day to get it in. Also had similar esc issues when an egr was starting to fail, took the dealer a week to get that in. First time i had an issue i was 800 miles from home, it would clear it self and never actually limited me.

Good thing about owning a GM product is there are so many dealers you can go to when on the road, i believe you can also get some priority when traveling. Being the dealer can clear it you could also have another do the same as it should show your waiting on repair parts.

I personally wouldn’t worry.
One guy said after clearing his codes 3 times they system would no longer allow him to clear codes!
 

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Discussion Starter · #5 ·
I have heard of DEF tanks being on back order for the HD trucks on and off since DEF has been introduced, I don't know if they have been able to increase the regional warehouse stocking? :)
One dealer told me that there was a nationwide backorder list of 8000 DEF tanks! One site indicates the DEF tank uses a new chip, and that is the holdup now. Looks like the chip shortage is holding up delivery of new trucks, and repairs. Sure wish I could find a workaround. I may try topping off the DEF tank each time I get diesel and hope the DEF level sensors never get read and then can never trigger the warning. BTW, 3 of the dealers I talked to all have customer trucks sitting on their lots waiting on DEF tank replacements. My situation could be worse since mine is still drivable at the moment.
 

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Unfortunately my 2021 hd3500 with 33,000 miles has been at the dealer for over a month....tank or wire harness? I have been told tanks can be 6 months out from a parts dealer... total BS. We had a 2020 that had problems around 30,000 then again around 50k so we traded it in for the 2021....If I didn't need the diesel to haul things I would be done with them....
 

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Purchase an Edge Insight CTS3 or Banks iDash monitor and clear the codes yourself. I was in your same boat with a DEF heater failure a few years ago and it was backordered for a few months. The dealer cleared the code a couple times. Mine never went to limp, but I also didn't want to keep returning to the dealer to clear the code. I told the service manager I'll just start clearing it myself if it returns. He didn't have an issue with it as long as it was the same single code. I did have to clear it a few more times prior to my heater coming in and them swapping it out - and I haven't had that issue return. So, I was able to clear the same code more than 3 times. Not sure if that aspect of a '21 is different than a '16?
This could be a workaround option...plus you can monitor so many other parameters through the CTS3 or iDash...
 

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Purchase an Edge Insight CTS3 or Banks iDash monitor and clear the codes yourself. I was in your same boat with a DEF heater failure a few years ago and it was backordered for a few months. The dealer cleared the code a couple times. Mine never went to limp, but I also didn't want to keep returning to the dealer to clear the code. I told the service manager I'll just start clearing it myself if it returns. He didn't have an issue with it as long as it was the same single code. I did have to clear it a few more times prior to my heater coming in and them swapping it out - and I haven't had that issue return. So, I was able to clear the same code more than 3 times. Not sure if that aspect of a '21 is different than a '16?
This could be a workaround option...plus you can monitor so many other parameters through the CTS3 or iDash...
Glad to hear you could clear the code multiple times. I tossed my code reader in my glove box so I will have it if it happens again. Seems like a good workaround. That is sure the kind of advice I was hoping to hear. I called today and there is still not even an estimated ship date for the new tank, so it will be at least 4 months!
 

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Unfortunately my 2021 hd3500 with 33,000 miles has been at the dealer for over a month....tank or wire harness? I have been told tanks can be 6 months out from a parts dealer... total BS. We had a 2020 that had problems around 30,000 then again around 50k so we traded it in for the 2021....If I didn't need the diesel to haul things I would be done with them....
Seems GM should be liable for some type of compensation. Sure is an expensive piece of yard art at the moment. If mine wasn't set up for my slide in truck camper and also with a hidden 5th wheel hitch, I would push my dealer to loan me a replacement until mine is fixed. Still tempted to do that.
 

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I made the same trip to Michigan's upper peninsula three times. On the way home during the third trip the def tank went from five bars down to def tank empty limited power will start soon all within 175 miles. I went to a station 10 miles down the road and filled the tank and it only held 2.9 gallons of def. That being said I was only 12 miles from completing my third trip and the def used was within 0.2 of gallon compared to the first two trips. I took it to the dealer and they basically said I won't get any better accuracy on the def tank. I not happy with this response at all.
 

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Disappointing to see the number of posts since Def was first introduced,of inaccurate readings of the DEF level causing owner concerns and unnecessary trips to the dealer. I guess GM is spending all their time developing enhanced super cruise so that we can be oblivious to the emissions controls while we are watching the Green Dream propaganda.

The level control meaurement in the Def tank should have been changed years ago.:)
 

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Disappointing to see the number of posts since Def was first introduced,of inaccurate readings of the DEF level causing owner concerns and unnecessary trips to the dealer. I guess GM is spending all their time developing enhanced super cruise so that we can be oblivious to the emissions controls while we are watching the Green Dream propaganda.

The level control meaurement in the Def tank should have been changed years ago.:)
The new 'indicator' (it' doesn't quality as a gauge) made it worse instead of better.

It also tries to indicate range remaining (sorta like the 'fuel range' page on the dic.

If running the same loads all the time, it's kinda/sorta ok.
If much of tank was run as daily driver, and then it gets worked hard -- the range estimator part seems to drops the indicator quickly.
Second problem is that all the segments on the gauge are not equal (and the middle isn't 'half full').

20+ 6.6 has the new indicator.
It also has a 7.0 gallon capacity DEF tank.

1/2 full on the indicator says it will take 2.5 gallons.
If engine loading hasn't changed, it should be kinda/sorta close.

With with the last full segment still on -- supposed to take 4.5 gallons. (so still has 2.5 gallons in it?)

Kinda wish it was like the 2011-- and no level indicator. ((in 2012 they added the 'DEF Level OK' message for above 30% and gave a % remaining below 30%, but still also gave the 1000/300 mile warnings.
When the 1000 mile warning (and/or 300 mile warning) came up --add some.

Different tank size, but similar gauge segment vs level vs range issue with the 3.0L trucks.
3.0L holds 5.3 gallons, same as the LML's.

Font Parallel Number Rectangle Pattern
 

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My 2021 Duramax with 20K miles randomly gives me the "DEF tank empty" and threatens to reduce my speed. It usually clears itself after a few miles but did go into limp mode once. On that occasion I had the codes cleared and it was fine after a few miles. We are planning a trip to Alaska and don't trust my new truck! I realize many people have gotten this error. My local dealer says I need a new DEF tank, but I have been waiting 3 months and still have no delivery date as it appears this is a common problem and there is a supply issue. I think I understand that this is an issue with the tank heater somehow interfering with the DEF tank gauge sensors. Are others having problems getting a DEF tank, or have others found a work-around for this (besides doing a delete which I am not going to do on a new truck!)?
I wonder if has a harness issue?

Presumably the verified it is the tank before ordering one -- but sometimes 'backorder' is in place to try and ensure full diagnosis gets done instead of 'repair by swapping expensive parts'.




Faulty Emission Reduction Fluid Tank Heater
February 10, 2021
The Emission Reduction Fluid Tank heater may be faulty on some 2020 Silverado 1500, Silverado 2500HD/3500HD, Sierra 1500, Sierra 2500HD/3500HD; 2021 Tahoe, Suburban, Yukon and Escalade models equipped with the 6.6L Duramax diesel engine (RPO L5P) or 3.0L Duramax diesel engine (RPO LM2). If the Emission Reduction Fluid Tank heater is not operating properly, there may be a Service Emission System/Service Exhaust Fluid System message on the Driver Information Center along with an illuminated Check Engine MIL. DTCs P20BB (Reductant Heater 1 Control Circuit Low Voltage) and P20C3 (Reductant Heater 3 Control Circuit Low Voltage Test Status) also may be set in the Engine Control Module (ECM).
The faulty Emission Reduction Fluid Tank heater may be caused by the tank heating elements being exposed to Diesel Exhaust Fluid (DEF) and shorting to the pump ground. Within the Emission Reduction Fluid Tank is the Emission Reductant Fluid Supply Pump Module, which contains an electrically operating reductant pump; reductant level, quality, and temperature sensors; and reductant system heaters. (Fig. 16) The reductant control module is mounted outside the tank.

Fig. 16

To determine if there is a short to ground, measure resistance at the Emission Reductant Fluid Supply Pump Module (Fig. 17), which would indicate that the heater has been exposed to DEF.

Fig. 17

TIP: Be sure that the DEF tank is at least half full of DEF before performing the resistance measurement.
With the Emission Reduction Fluid Tank wiring harness disconnected, measure resistance from pin 9 to pin 14 using a Digital Multimeter. Next, measure resistance from pin 10 to pin 14. The illustration (Fig. 18) shows pin 9 (#1), pin 10 (#2), and pin 14 (#3).

Fig. 18

If either resistance reading is less than 10M ohm, the heater is faulty and the Emission Reduction Fluid Tank should be replaced. If both resistance readings are greater than 10M ohm, continue with diagnostics according to the appropriate Service Information.

Cold Weather Operation
The two reductant (DEF) heaters are designed to thaw DEF that has become frozen in temperatures below 32°F (0°C) in the Emission Reduction Fluid Tank and supply line to the DEF injector. The reductant control module monitors the reductant temperature sensor located within the Emission Reduction Fluid Tank in order to determine if reductant temperature is below its freeze point. If the control module determines that the reductant may be frozen, it energizes the reductant heaters. Reductant pump operation is disabled for a calibrated amount of time to allow the heaters time to thaw the frozen DEF.
For more information, refer to Bulletin #21-NA-002.
 

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Discussion Starter · #14 ·
After getting nowhere for 3 months and having a new truck that was nothing but $70K yard art, I googled GM Lemon Law. The first hit was a page that said please contact GM first and gave an email and phone. I email them at [email protected] and told them my issue and that I wanted a definite date within 2 weeks when my truck would be repaired, or a guarantee they would cover the cost for a tow and a rental vehicle, or they could replace my truck with a new one. GM called the next day and I have an appointment this week to get my DEF tank replaced! Guess the squeaky wheel does get greased.
 

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It would be interesting to know how scared GM is of LemonLaw applicants...if that really is a motivator if you qualify, or if it's just another issue to ignore for them. what does everyone think?
 

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My 2021 Duramax with 20K miles randomly gives me the "DEF tank empty" and threatens to reduce my speed. It usually clears itself after a few miles but did go into limp mode once. On that occasion I had the codes cleared and it was fine after a few miles. We are planning a trip to Alaska and don't trust my new truck! I realize many people have gotten this error. My local dealer says I need a new DEF tank, but I have been waiting 3 months and still have no delivery date as it appears this is a common problem and there is a supply issue. I think I understand that this is an issue with the tank heater somehow interfering with the DEF tank gauge sensors. Are others having problems getting a DEF tank, or have others found a work-around for this (besides doing a delete which I am not going to do on a new truck!)?
You have just defined the reason I own an LMM series vehicle. NO DEF. It has been a PITA ever since it was introduced in 2011 and they have not gotten it right yet!

Months and months of waiting for parts on a new 70-90,000 truck is WRONG!!
 

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We don't have lemon laws in Canada but I have to agree that having to threaten to use the lemon law is not the way business should be run. IMO there is absolutely no reason that GMC et al choose not to stock a reasonable supply of parts for not just new but used vehicles as well. They prioritize the building of new vehicles but the just in time delivery of parts doesn't work in the new global economy and hasn't for years now so inventory costs money but so do unhappy or lost customers.🤔
 

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It would be interesting to know how scared GM is of LemonLaw applicants...if that really is a motivator if you qualify, or if it's just another issue to ignore for them. what does everyone think?
Their not scared. I believe their attitude is- "If you don't like it, go somewhere else, we don't care."

They sure don't communicate in a way to make people think otherwise. Whereas some (not all) other manufacturers will do the right thing, even if it costs them millions or billions of dollars of revenue to correct their mistakes.
 

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Discussion Starter · #19 ·
Just to clarify, I did not threaten to use the Lemon Law. One of the hits when I googled Lemon Law was the GM Customer Care site, along with a lot of lawyer sites. I chose to contact GM Customer Care first and they immediately responded by email and phone, and I have an appointment this week to get my truck fixed. My opinion is that someone up the chain is attempting to correct the problem with my truck. I wasn't confident my local dealer was doing his part to resolve my issue. Yes, the DEF tank issue needs to be corrected for all trucks, but I am giving GM the benefit of the doubt, and my local dealer sure didn't earn my future business. Been buying GM for 40+ years and don't plan to change.
 

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Glad to hear you could clear the code multiple times. I tossed my code reader in my glove box so I will have it if it happens again. Seems like a good workaround. That is sure the kind of advice I was hoping to hear. I called today and there is still not even an estimated ship date for the new tank, so it will be at least 4 months!
Has anyone else been successful to clear the code multiple times on a 2020+? Before I pull my truck back from the dealership, I'm curious to know the confidence in this. My error also cleared itself several times before going into the permanent count-down mode. I have not tried clearing it with a scan tool. But I've been waiting now two months for the dealer to get a part, and they have no ETA at all. Getting desperate.
 
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