Duramax 6.6L Service Exhaust System…. Most Common Repair P21DD P20B9

Reductant tank heater 1 is a common failure causing vehicle to enter limp mode, requiring DEF tank reservoir replacement.
Duramax P21DD P20B9
#automotive #cars #knowledge #mechanic #diesel

[@cavy16262]

I needed the tank heater done while in Wyoming past July! Thank goodness the shop had a day to do it! Thanks to the mechanics, who are now electronic wizards too, for keeping my 2015 Duramax running. Now, if only the government would get its head out of its backside, we wouldn’t need all this additional exhaust bs! Eliminate regen, eliminate DEF, eliminate pollution controls and let the diesel BREATHE

[@DadsGarageDiagnosticSpecialist]

Thanks for commenting. Yes, these seem to fail always at the worst possible time and leave you stranded… And because of the emissions controls, you have no choice. Starting around 2007 is when all of these problems really took off and we started seeing these diesel emission systems and even diesel fuel systems failing at an alarming rate… All in the name of emissions and scraped from the back of consumers.

[@DadsGarageDiagnosticSpecialist]

Thanks for commenting EDDIE. Most of the time this repair is free to the customer covered by a Special Policy extended warranty. Outside of warranty this repair is about $900-$1200 parts and labor out the door.

[@watchmanexpert]

@@DadsGarageDiagnosticSpecialist Question I want buy the new 3.0 Duramax but I keeps always my trucks for 15 years all my truck I had was v8 gas , this 3.0 will be my first diesel and I don’t know nothing about diesel… my question is the truck can last 15 years with out big problems? And if the truck has big problems with DEF approx how much is the repairs ? 5 k. 10 k I heard in KZbin can be very expensive the DEF system repair … I am good with maintenance

[@DadsGarageDiagnosticSpecialist]

@@watchmanexpert I haven’t been impressed with the 3.0L, it is packed very tightly into the engine compartment and even minor repairs take hours of work….although the only real problems I’ve been seeing usually involves the DEF system. Also not impressed with the belt driven oil pump at the back of the engine, requiring transmission removal to replace the belt every 100k miles. I would recommend leasing a truck with the 3.0L rather than buying, diesel ownership can be very very expensive….. and it’s not worth it unless your diesel truck is making you money every day and if you’re using a half ton truck for working, the gas engine can do everything the diesel can, but cheaper and more reliable. That being said I do like how smooth the 3.0L runs and it does run nice and pull nice while driving. Overall I would recommend a gas engine due to lower maintenance, upkeep, and repair costs. Thanks Tony. Good question.

[@watchmanexpert]

@@DadsGarageDiagnosticSpecialist thanks for take you time and help me , with gas motor is better for long term ? 5.3 Silverado ?

[@thejayjaybe]

Love this video, so good! Thanks for posting it. I'm dealing with a P249d code, but still trying to troubleshoot whether it's the injector, or a faulty NOX2 sensor. My scan tool is an Innova 5160RS (or 5610, same thing), and I have figured out how to command a DPF regen, but cannot figure out how to command a reductant fluid quality test. Any ideas? Maybe I've got to return this scan tool and try something else, not sure yet. Watching some live data it looks to me like the downstream NOX2 sensor is a little suspect. Worked almost normal after yesterday's regen, at least for a mile of driving post-test it looked like the system was working and NOX2 was only 10% or 20% of NOX1. I just want to pinpoint the problem before buying that NOX2 sensor which is close to $400, if it turns out the injector is actually the culprit.

[@DadsGarageDiagnosticSpecialist]

Thank you very much! The goal of the SCR system is to maintain NOX levels at least 70% lower on the outlet than the inlet so if you are seeing Nox 2 reading 10%-20% that is a good thing. Not all years of Duramax will have the fluid quality test available… They will call it something else like malfunction indicator test or tamper test. Otherwise try a different scan tool. Also check out this short video: kzbin.info/www/bejne/jpvJnpivn5t9rKcsi=l7oqgHOUp94FqGQ7

[@stephenauer9116]

What codes normally equal this problem? I have codes p20e8 and p20e9 currently. I thinking the pump or the injector nozzle

[@DadsGarageDiagnosticSpecialist]

Thanks for commenting Stephen. This failure in this video usually results in P20B9 and/or P21DD. P20E8 = DEF pump pressure too low P20E9 = DEF pump pressure too high I’d take a look at the hoses on the reservoir for being pinched/mis installed or possible one of the seals isn’t seated properly and causing a blockage or allowing the pump to suck air. This can be seen in the video 4:38 .

[@rvspecialistgoshen]

Great video! We are having issues with our 2020 Duramax DEF system. We are getting code P20C1-00 Reductant Heater 3 Control Circuit. Would you have any advice you could offer on how to go about fixing this issue?

[@DadsGarageDiagnosticSpecialist]

Thank you for the comment RV Specialist. There is a bulletin for this code, check out PIP5838B regarding certain replacement DEF tank wiring harnesses being built wrong. Other than that P20C1 is for the DEF tank heater which is part of the pump assembly and I have seen some of those fail also. Let me know if I can assist further.

[@HenryGarcia-uj4kf]

What should I do I got a 2017 gmc sierra and it’s showing it’s says low def speed limit soon but I know I have def in it

[@DadsGarageDiagnosticSpecialist]

You need to know what code is causing the fault message. Thanks.

[@molsoncanadian99]

What year truck is this? My 2018 is throwing a P20B9, only when its -10c or below. So pretty obvious its the heater. Can you share the part number?

[@DadsGarageDiagnosticSpecialist]

I can’t remember what year this one was. I’ve seen this failure on just about every year. I don’t have the part number unfortunately. The part numbers are constantly being updated too. Thanks.

[@juanc.landscaping2765]

I got a code p20bd, currently on limp mode, will replacing that part in the video fix the issue. It shows reductant heater B when i check the code.

[@DadsGarageDiagnosticSpecialist]

That is a possibility yes. Very common in my experience. Thank you.

[@21_d51]

What codes did you get Im getting P0406 and it says service exhaust fluid system

[@DadsGarageDiagnosticSpecialist]

This vehicle had a P21DD for Reductant tank heater 1 current too low. P0406 is for an exhaust gas recirculation valve position sensor circuit high voltage detected. This is an electrical circuit fault code so most likely a disconnected or faulty sensor or possible wiring damage. Thanks for commenting 21_d

[@JM-cb5pp]

I did the exact same replacement. However the code does not show up because it was replaced. The cluster still shows the def light and mph is still limited. Does the dealer have to reset?

[@DadsGarageDiagnosticSpecialist]

In some cases yes it will need to be reset with a scan tool… there isn’t actually a command to reset. The vehicle must see the system circuits operate normally and pass its internal self tests before the message will clear. After replacing the reservoir I use the scan tool to command the exhaust fluid heater on for 60 seconds. That should clear the message. Otherwise you’ll have to wait for the vehicle to test and pass itself which may take a long time or may not happen at all depending how severe the warning level on the cluster has gotten. Thanks.

[@saulnev-z4196]

I took my truck in to the dealer for the same problem, replaced the def pump and now it shows low def and max speed 65mph, and supposedly an exhaust code now!

[@DadsGarageDiagnosticSpecialist]

Hi Saul, thanks for commenting. What codes does it have?

[@eliasmadrigal8416]

What cost effective scanner can I get to help read and clear these codes?

[@DadsGarageDiagnosticSpecialist]

There are many options. A lot of these codes and fault messages cannot be erased though. Try Autel or Top Don. Thanks for commenting.

[@christopherbradley5456]

How do I get the warning level 5 to clear? What test is needed? I’m at 4miles. I have a GM tech 2 scanner. I wasted $1400 at a shop with no luck. Any advice please.

[@DadsGarageDiagnosticSpecialist]

The only way to clear it is to properly fix the vehicle and get it to run and pass its self tests. If the ECM has an update available a reprogram will clear it out for a short time too. Otherwise a new ECM and then you’ll have to fix whatever originally caused it. You shouldn’t really need to replace the ECM though, it just needs to be evaluated. Check out this video: “Duramax 4mph, no codes” kzbin.info/www/bejne/jpvJnpivn5t9rKcsi=aa7icDJlrWjdj0qy Thanks.

[@christopherbradley5456]

Originally it was reductant heater 1. Getting 2 ohms after replacing. Turn on each heater all ok. A low coolant replaced both thermostat. (Now I’m getting no def pressure.) Could it be def injector clogged. I don’t think it clogged bc of no pressure.I checked the seals. I hear pump leak down test. Soot at 2%. Thank you I watch that video

[@DadsGarageDiagnosticSpecialist]

If the DEF pump won’t build pressure. You need to take the pump back out and see if you smashed the O-ring or pinched the hose inside the tank.

[@christopherbradley5456]

Okay thanks. After confirming. Which do I run first Leak down or quality fluid test? Should Leak down test be command on without truck run? When should I start seeing pressure buildup? After confirming. What is my next step? If no pressure after confirming those steps. Can a def injector cause no pressure also?

[@DadsGarageDiagnosticSpecialist]

@christopherbradley5456 ​​⁠do the leak test first and make sure it builds 500kpa/70psi within 5 minutes and inspect for leaks which could appear as white crystals or dripping DEF. I have a few Duramax videos. Check them out. The DEF injector failing is rare.

[@ddrowdy2]

Mine went out, bought a cheapo off Amazon, lasted 1 year then I got the Bosch, been going 2 years now.

[@DadsGarageDiagnosticSpecialist]

Bosch is the supplier for a lot of parts for most manufacturers so you can’t go wrong with that. Thanks.

[@derekddurbin]

Mine is doing this only has 30k miles 2016 2500HD LTZ Z71 6.6L duramax allison transmission put 5 gallons in def tank and it’s still saying in 30 miles it’s gunna be 55mph max speed how do I reset it manually?

[@DadsGarageDiagnosticSpecialist]

You would need to check the codes and find out why the system is in restriction. If it was simply a fluid level restriction, then driving the vehicle on the highway should solve the problem. Thank you for commenting. Let me know if you need further assistance.

[@derekddurbin]

@@DadsGarageDiagnosticSpecialist I disconnected both batteries hoping it would reset but it didn’t and I know the tank is full, this may be a dumb question but under the hood there’s a 110v 3 prong adapter I was told that I need to plug that in sometimes but never do, what’s that for? And can that have anything to do with it or is it just something I have to drive for awhile and hope it clears? Thanks for responding I really appreciate it

[@DadsGarageDiagnosticSpecialist]

Disconnecting the batteries won’t reset the warning message, the ‘only’ way is to get the ECM to run and pass its self tests. It helps when there is a code stored, but sometimes when I get them for diagnostics the code have been erased so it requires a full system test to establish where the start. The 110V cord under the hood would not have any relation at all to the problem, that is the block warmer for extreme cold climates to help the engine start when cold. Not needed unless you’re seeing temperatures down to about 0F.

[@derekddurbin]

@@DadsGarageDiagnosticSpecialist ok thanks for your expertise brother I really appreciate it

[@DadsGarageDiagnosticSpecialist]

@@derekddurbin of course!

[@bradleyt3820]

Whats that small oring for? Couldn't tell what you did with it. Also ever heard of a pump only running backwards into the tank?

[@DadsGarageDiagnosticSpecialist]

Thanks for commenting Bradley. I guess I didn’t show that part very well. The small O-ring goes on the exhaust fluid pump, I find that installing it onto the pump rather than the reservoir prevents the o-ring from being crushed. The pump is designed to run backwards at times to drain the exhaust fluid from the lines as well as air bleeding. What other symptoms do you have going on? Any codes? I’d start with commanding an exhaust fluid leak test with a scan tool, exhaust fluid pressure should reach at least 72psi/500kpa.

[@bradleyt3820]

@@DadsGarageDiagnosticSpecialist p204f-00 I have scan tool hooked up commanding the pump to turn on. It runs but no pressure. Ran pump out of a jar and its definitely only running backward. Filter not plugged. New pump. New little controller on top of tank for temp. Is the purge valve built into the pump? How do I test it? Scanner lets me turn it on and off but don't know how to verify it's working correctly.

[@bradleyt3820]

@@DadsGarageDiagnosticSpecialist also thank you for replying

[@DadsGarageDiagnosticSpecialist]

The purge valve is part of the pump and is an ON/OFF valve. When ignition is turned off the purge valve and the exhaust fluid injector opens, then the pump runs backwards to suck the exhaust fluid out of the hoses to prevent freeze up and crystallization. P204F sets when the ECM is unable to build any exhaust fluid pressure. It’s important to command a leak test with the scan tool, not just command the pump to run. Usually I find P204F caused by a pinched reservoir hose or crushed seals between the pump and reservoir. See 4:40 in the video.

[@bradleyt3820]

@@DadsGarageDiagnosticSpecialist I've checked all that multiple times already.. not my first time working on these just the worst time lol. when I do leak test the pump runs and everytime the injector pulses I can see air bubbles enter into the pump which also confirms to me the purge valve is being activated when it's not supposed to be causing the pump to run in reverse. Do you know which pin on the pump connector controls the purge valve? I'm at the point where I'm almost certain it's a wiring or ecm issues.

[@georgep.8478]

What did you do? Test the reductant heater? Test nox sensor?

[@DadsGarageDiagnosticSpecialist]

The Nox sensor is another common failure, however this repair is a Diesel exhaust fluid tank reservoir replacement. The reservoir contains DEF tank heater 1, and since DEF is corrosive that is usually the one that fails. Very very common failure. I replace three or four of them a week sometimes. Thanks for commenting.

[@gustavomaya8999]

I did this same thing but the warning won’t go away, it still doesn’t let me go over 55mph. Any help?

[@DadsGarageDiagnosticSpecialist]

Hi Gustavo do you have any codes before and after repair?

[@gustavomaya8999]

@@DadsGarageDiagnosticSpecialist it had codes p20E8 P205B P20B9 those codes are now gone but that warning doesn’t go away?

[@DadsGarageDiagnosticSpecialist]

If you have no codes returning you will need to use a scan tool to run a malfunction indicator test or it may take a lot of driving under mixed conditions, but that depends what warning level you are at…if you’re limited to 55mph you will likely need a scan tool. The ECM must run and pass the associated self-tests before it will exit restriction mode.

[@gustavomaya8999]

@@DadsGarageDiagnosticSpecialist right now it just says it has 10milles before it’s Max speed goes to 4mph. I’ve tried everything but that warning just won’t go away. Do you think I should keep on running it or should I stop?

[@DadsGarageDiagnosticSpecialist]

At this point you will definitely need a scan tool.

[@truckerman9836]

No music while turning wrenches all day would drive me crazy.

[@DadsGarageDiagnosticSpecialist]

Hearing the same song 10 times in one day drives me crazy. It’s not always silent lol. Thanks for commenting.

[@gizmoking1000]

What is the average cost of this fix

[@DadsGarageDiagnosticSpecialist]

About $700-$1000 parts and labor including diagnostics. There is an extended warranty so check if you’re covered. Thanks.

[@andrewramirez9428]

Would this be for the code p1050 man??

[@andrewramirez9428]

My truck is an 18 3500hd man for more info on it, im bout to drive 10 hours and my truck just threw that code I’m hoping it’s not going to go in limp mode on me!

[@DadsGarageDiagnosticSpecialist]

P1050 would be for reductant tank level sensor malfunction. Yes I’ve seen some failures and the repair is near identical to the one in this video, but slightly different design. Most likely this will cause limp mode if ignored long enough.

[@andrewramirez9428]

@@DadsGarageDiagnosticSpecialist thank you for the fast reply man!! Do you think it’s possible it’s just a loose electrical connection or the reductant control module? Because when I check the def level gauge when the code went off it was “- -“ but then switched to “ok” and then back again.

[@DadsGarageDiagnosticSpecialist]

@andrew ramirez I’ve seen some failures of the level sensor which is all part of the reservoir assembly. There is no float because exhaust fluid is corrosive and also crystallizes in contact with air. Edit: there is no float on older models, but the newer models have a magnetic float sensor, but does not work the same as typical float sensors.

[@andrewramirez9428]

@@DadsGarageDiagnosticSpecialist I really appreciate you getting back to me man!! I took the cover off the def tank and cleaned out all the harness connections with electrical cleaner and put some dielectric grease in the plugs. I actually even bought the assembly for $1200 just incase that didn’t fix it. Drove 9 hours to MO and the check engine light finally turned off when I got to MO! So I’m hoping that’s All it was causing that code was the dirty plugs but we’ll see hopefully before I return that part.

[@ivanlopezlopez952]

P249D? Why would that code come up. On a 2018 Duramax Allison transmission 3500hd ltz dually 138k miles

[@DadsGarageDiagnosticSpecialist]

Thank you for commenting. There are a few things that can cause P249D…. Check out my related video here: kzbin.info/www/bejne/jpvJnpivn5t9rKc Most often the cause is faulty NOX sensor readings, faulty EGT sensor readings, restricted indirect injector, etc. Also check out these videos for more information about indirect injector….Duramax 6.6L P0420 code diagnosed from the driver seat - faulty indirect injector kzbin.info/www/bejne/nHKWlmmkaMmliNU Duramax P0420 second opinion saves customer a lot of money! kzbin.info/www/bejne/gnKxYaqipqlsabM

[@ivanlopezlopez952]

Do I have to delete the truck to make the code go away? Thank you for your help 🙏🏻

[@DadsGarageDiagnosticSpecialist]

A delete and tune would eliminate the problem yes, however that is not possible in every location due to emissions testing and registration requirements, etc. The preferred fix is to diagnose and repair the system as it is designed and maintain emissions systems in working order. Thanks.

[@ivanlopezlopez952]

@@DadsGarageDiagnosticSpecialist ok.. so what would be the best/quickest solution? Other than deleting the truck? Should I do nox sensor or indirect fuel injector? Thanks a lot for your help man

[@DadsGarageDiagnosticSpecialist]

@@ivanlopezlopez952 the NOX 2 sensor is the most common, NOX 1 also suffers from frequent failures so those would be fairly easy to test with a capable scan tool and a road test. The first video I linked to you is the process I would follow if the NOX sensors were confirmed to be working ok. I’d run the self test and depending on results we would decide what to do about it. Duramax 4mph restricted max speed. No codes? kzbin.info/www/bejne/jpvJnpivn5t9rKc Most likely you’ll be better off paying to have it diagnosed rather than replacing parts, most of the related parts are expensive. Thanks.

[@henryrodriguez1131]

P20c3 code?

[@DadsGarageDiagnosticSpecialist]

This one had P20B9 and P21DD codes related to reductant heater 1...I just updated the title and description. P20C3 is related to reductant heater 3, located at the reductant pump assembly. So you will probably need to remove the DEF tank and test that heater resistance and possibly replace the pump. Thanks.

[@mikefenner7422]

P20b9 any ideas

[@DadsGarageDiagnosticSpecialist]

Most likely a faulty the same failure in this video. The tank reservoir contains reductant heater 1.

[@briseidapalominos8192]

Hi! I have 2015 Silverado 3500 duramax and getting a P20BB code saying reductant tank heater 1 low circuit. Any idea? We just replaced the def tank too! TIA!

[@DadsGarageDiagnosticSpecialist]

That code is for the DEF heater 1 which is located in the DEF tank so I’d be suspicious of wiring faults.

[@briseidapalominos8192]

Thank you so much for the reply.

[@briseidapalominos8192]

One last thing, since we had just replaced the def tank heater and went and got another replacement and still have the code showing up the wiring we should be looking at would be the def pump? Also i got a freeze frame data p20bb code not sure if that means anything. Thanks so much for your knowledge. I appreciate ya!