Cleared it with my tuner and was back after 2-3 starts. P21DD Reductant heater 1 current too low The GPCM (glow plug control module) is what detects the heater open circuit in the heater which monitor voltage to the 3 diesel exhaust fluid heaters (DEF), Please log inor registerto add a comment. I have a P21DD Permanent DTC code. How to repair code P21DD in 2013 Duramax - YouTube 0:00 / 8:52 How to repair code P21DD in 2013 Duramax Master Tech 221 subscribers Subscribe 137 89K views 7 years ago Duramax repair,. The codes are c0131, p21dd, and p128e. there is a very small piece of debris on the screen, not ferrous. ” It mostly happens due to a defect in the reduction tank heater used to heat the DEF. P21DD P20B9 Limp mode (will appear on heads up display) Replacement Options There are three heaters located through the DEF system and all are prone to failure. I had the check engine light come on. What Does the P21DD Code Mean? The Selective Catalyst Reduction (SCR) system reduces Oxides of Nitrogen (NOx) emissions by injecting a metered amount of Diesel Exhaust Fluid (DEF) or reductant into the exhaust gas stream entering the SCR catalyst. It appears to be a DEF tank heater issue, but I cant find much info about it. 4548 Views 3 Replies 3 Participants Last post by maxinDixon, Feb 4, 2021. P21DD Reductant heater 1 current too low. - 2020 - CRC - 10/26/20 Page 2 October, 2020 Bulletin No. However, the pump actually flowed 20% less fuel than its CP3 predecessor. The check engine light comes on when I Ask an Expert Car Questions Wolfgang, Master Auto Tech 6,720 Satisfied Customers Master, L1, L2, ASE 15yrs and running. replaced the heater went to reset with Verus , still in limp mode. The Selective Catalyst Reduction (SCR) system reduces Oxides of Nitrogen (NOx) emissions by injecting a metered. 2014 Chevy Cruze Clean Turbo Diesel 202K (Domenic), 1986 Mercedes 300E 5 Speed odo broken (Rammstein - Sold and then repurchased), 2017 Honda Civic Sport Hatchback 6M 7K (Gordon), 2004 Mercedes S430 4Matic 187K (Kevin) - Going to be the daily grinder for now, but I still love my Cruze!! Just threw my first CEL, a P21DD code at 67K. if he dont have the part hell get one from another dealershipAlso said it is covered under warranty and will give us a rental car if he keeps it overnight !!!I have 48917 miles on my cruze. Each time I erased it, the service engine light turned off (even though the permanent code remained). Code P21DD GMC Description. P21DD Reductant heater 1 current too low The GPCM (glow plug control module) is what detects the heater open circuit in the heater which monitor voltage to the 3 diesel exhaust fluid heaters (DEF), Please log inor registerto add a comment. Reductant heater replacement. The dreaded P21DD (reductant heater open circuit) reared its ugly head last Saturday. It says Im going to go in limp mode in 106 miles. I had the check engine light come on. Im not looking forward to dumping $500+ into a car that is less than 2 years old. the - Answered by a verified GMC Mechanic We use cookies to give you the best possible experience on our website. Scanned it, DEF heater code. Cruze Diesel DEF Reservoir Heater Failures – IDParts Blog. Im guessing you are getting the p21dd code? You should get a long count down and then you will get speed limited to 65 I think then it will keep dropping after so many miles. P21dd Code 2014 Duramaxfirst time was under warranty this time I am afraid it will not be covered. If you’re experiencing this code, it’s important to find a mechanic who can. 2015 LML CEL - P24C4 : r/Duramax My dad’s 2015 Duramax just threw code P24C4 yesterday. The codes are c0131, p21dd, and p128e. Duramax LML CP4. Scan for codes retrieved one code-p21dd. By tirengolf. 4 Posts. If this condition is not found, refer to normal SI diagnostics GM bulletins are intended for use by professional technicians, NOT a do-it-yourselfer. Duramax P21DD DEF Heater Reservior Replacement TruckNerd 22K views 3 years ago You Have Been Filling Your DEF Tank Wrong Since Day 1: How to Fill Diesel Exhaust Fluid Tank ⛽ Thoroughbred Diesel. Engine has around 175k miles and is completely stock. Used scan tool to command all heaters on-heater #1 is operating in spec again. P21DD Code Meaning, Causes, Symptoms, & Tech Notes. 2014 Chevy duramax starter replacement - YouTube 0:00 / 0:17 2014 Chevy duramax starter replacement Calvert County Buck Wild 13 subscribers Subscribe 7 3. The GPCM (glow plug control module) is what detects the heater open circuit in the heater which monitor voltage to the 3 diesel exhaust fluid heaters (DEF), 0 votes. So I went out to my truck to start it this morning and check engine light came on. After 3 separate restarts the CEL was back. 61000 miles on 2015 Duramax. That being the case, I called a dealership in southern Tennessee and made an appointment to confirm the issue. I never anticipate needing the DEF tank heater due Ask an Expert Car Questions GMC Questions Pete, GMC Mechanic 44,832 Satisfied Customers GM training and dealer tech for 14+ years. Scan for codes retrieved one code-p21dd. 61000 miles on 2015 Duramax. The P21DD trouble code on Duramax means “Low Current in the Reduction tank Heater. What Does the P21DD Code Mean? The Selective Catalyst Reduction (SCR) system reduces Oxides of Nitrogen (NOx) emissions by injecting a metered amount of Diesel. I have searched the internet trying to find this exact code, but I cant find. I have a 2014 Silverado 3500HD DMax and received a letter from Chevy in late 2016 about this problem. My 2015 Duramax is throwing P21DD code and P21DDpd code. My 2013 is at 53,000 miles,3,000 past emissions warranty. Oreilly checked it and came up with a P21DD code. Code P21ddJust called the dealership and he said bring it in Monday to replace the tank. Scan for codes retrieved one code-p21dd. Got the extended warranty letter, and had GM reimburse me for the. I just cleared the code and replaced it. • P21DD: Reductant Tank Heater 1 Low Current • P221C: Reductant Tank Heater 2 High Current • P10D9: Reductant Heater 1 Control Circuit Shorted • P10F3: Reductant Heater 2 Control Circuit Shorted Reductant Heater 2 Control Circuit • P143C: Reductant Heater 3 Control Circuit Shorted Reductant Heater 2 Control Circuit. 0votes answeredSep 10, 2021by OBDIITech(7. P262B Code Meaning, Causes, Symptoms, & Tech Notes. 2014 CTD Error Code P21DD Emission Reductant Tank. My 2015 Duramax is throwing P21DD code and P21DDpd code. How to repair code P21DD in 2013 Duramax - YouTube 0:00 / 8:52 How to repair code P21DD in 2013 Duramax Master Tech 221 subscribers Subscribe 137 89K views 7 years ago Duramax repair,. This would be the DEF…>I have a P21DD Permanent DTC code. TECHNICAL SERVICE BULLETIN 6. P21DD error >On my 2013 GMC Sierra 2500HD 6. answered Sep 10, 2021 by OBDIITech (7. My truck has code P21DD? My name is Nathan, I am hoping to get some insight on what code P21DD means. Scan for codes retrieved one code-p21dd. P2463 and P21DD I’ve been trying to clear the codes while driving so I can do a regen of the dpf system but it keeps going back into reduced power mode Julio Quispe Category: Chevy Satisfied Customers: 3,259 Experience: Automotive Technician at MBR Automotive Ask Your Own Chevy Question Chevy Mechanic: Do you have ability to command functions?. Had one of my good customers drive up in 13 GMC 3500 duramax in limp mode. I have a 2014 6. Sometimes a fault or defect in the control module of the tank triggers the P21DD. There are other helpful videos such as https://www. How to repair code P21DD in 2013 Duramax - YouTube 0:00 / 8:52 How to repair code P21DD in 2013 Duramax Master Tech 221 subscribers Subscribe 137 89K. Add to quote; Share Only show this user. Wolfgang is online now Related Car Questions Add def light is on. The connection inspection waa never mentioned on my reports the first two times under warranty. To handle the additional power capabilities of the engine the fuel rail pressure was increased to 30,000psi. The only replacement option is to. It first threw a P21DD code which was probably do to the DEF tank freezing. Duramax P21DD DEF Heater Reservior Replacement TruckNerd 22K views 3 years ago You Have Been Filling Your DEF Tank Wrong Since Day 1: How to Fill Diesel Exhaust Fluid Tank ⛽ Thoroughbred Diesel. I went to auto zone and the gave me the code P21DD. My name is Nathan, I am hoping to get some insight on what code P21DD means. This control module is located just above the heater tank. I have a P21DD Permanent DTC code. How to Fix P2263 Code on Duramax? (Completely Explained). 6l duramax and it has been…. the - Answered by a verified GMC Mechanic. These codes indicate a fault in the supercharger boost control circuit. How to fix code P21DD Reductant heater replacement on 2015. I just threw this code P21DD (Reductant Tank Heater 1 Low Current) today at 49k miles. Error code P21DD - Diesel Place : Chevrolet and GMC Diesel Truck Forums See less See more 2014 Chevy Cruze Clean Turbo Diesel 202K (Domenic), 1986. Next time I will do more testing. P21DD Chevrolet Code Meaning, Causes, Symptoms, & Tech Notes. Step 3: Inspect The Reduction Tank Heater Control Module. Napa code reader read P21DD. Took it to the dealer and they replaced it at no cost. have a P21DD Permanent DTC code. Looked online for the code and found EGR cooler bypass position sensor exceeded learning limit. Discussion Starter · Oct 15, 2017 Started out with Code P21DD, which came on as a permanent code that I couldnt erase coupled with one that I could erase. After obtaining the related fault code, take the necessary steps to eliminate it. 2015 Duramax is throwing P21DD code and P21DDpd code. 5708899 Inspect the Emission Reduction Fluid Tank electrical connector for any signs of damageand repair as necessary. My mechanic said the code was P21DD - Reductant Tank Heater and there was a bulletin on it. 2015 Duramax P21DD & P20B9. After checking the net and finding you guys and reading your stories, I decided I must have DEF problems. This would be the DEF tank heater. Disconnect and inspect C3613 (16 pin connector) at the reductant pump/heater assembly and C4851 (4 pin connector ) at the reductant level sensor/quality module for signs of corrosion. P21DD Chevrolet Code Meaning, Causes, Symptoms, & Tech Notes>P21DD Chevrolet Code Meaning, Causes, Symptoms, & Tech Notes. 7L - Illuminated MIL With DTCs P21DD, P204C, P21CD And/Or U02A2 - Built On Or Before 1-Aug-2018 19-2315 18 October 2019 Model: Ford 2017-2019 F-Super Duty Issue: Some 2017-2019 F-Super Duty vehicles built on or before 1-Aug-2018 equipped with a 6. My apologies to bump and old thread, but I hope a GM customer satisfaction representative is reading this regarding code P21DD on the 2014 CTD. BubbaA Discussion Starter · Jan 3, 2021. 6l duramax with codes c0131, p128e and p21dd. My 2015 Duramax is throwing P21DD code and P21DDpd code. I took it in and they cleared the code. 2015 Duramax P21DD & P20B9 41,814 views Feb 15, 2018 94 Dislike Share Save Will Brown 132 subscribers Reductant heater replacement. The codes are c0131, p21dd, and p128e. TECHNICAL SERVICE BULLETIN 19. What Is P21dd Code On Duramax: How To Fix?. Indicates problem with heater circuit in the def. Besides, some other minor electrical component failure can trigger this issue. - 2020 - CRC - 10/26/20 Page 2 October, 2020 Bulletin No. does anyone know if this code can be fixed by replacing parts yourself without a tech2 tool or will it require a tech 2 tool. 2013 Chevy duramax p21DD DEF heater replacement - YouTube 0:00 / 14:56 2013 Chevy duramax p21DD DEF heater replacement Bishop’s DIY Auto Repair 321 subscribers Subscribe 2. On my 2013 GMC Sierra 2500HD 6. code was read at NAPA store code was P21DD … read more Marc Mechanic Associate Degree 4,352 satisfied customers I have a 2015 LML Duramax. P01F0 code 2015 Duramax, Ive cleared the code multiple>P01F0 code 2015 Duramax, Ive cleared the code multiple. According to the letter from Chevy, the warranty on this item was extended to 10 years or 120,000 miles from date vehicle was put in service. The Selective Catalyst Reduction (SCR) system reduces Oxides of Nitrogen (NOx) emissions by injecting a metered amount of Diesel Exhaust Fluid (DEF) or reductant into the exhaust gas stream entering the SCR catalyst. Discussion Starter · #1 · Jan 3, 2021. The cost of diagnosing the P21DD GMC code is 1. 7L - Illuminated MIL With DTCs P21DD, P204C, P21CD And/Or U02A2 - Built On Or Before 1-Aug-2018 19-2315 18 October 2019 Model: -2018 equipped with a 6. My mechanic said the code was P21DD - Reductant Tank Heater and there was a bulletin on it. What are the Possible Causes of the Code P262B? Low battery voltage Reprogram Engine Control Module (ECM) Faulty Engine Control Module Engine Control Module harness is open or shorted Engine Control Module circuit poor electrical connection How to Fix the P262B Code? Start by checking the Possible Causes listed above. I failed to check the old heater readings after removal. Most auto repairs shops charge between $75 and $150 per hour. Diagnostic code P21dd state. How long is it covered under warranty and what else is?. Code Meaning, Causes, Symptoms, & Tech Notes>P262B Code Meaning, Causes, Symptoms, & Tech Notes. Use an OBD scanner to collect all related trouble codes, such as P0045 or P0046. This may be due to water intrusion within connectors C3613 and/or C4851 on the reductant harness going to the reductant. The P21DD trouble code on Duramax means “Low Current in the Reduction tank Heater. duramax p21DD DEF heater replacement. 2015 LML CEL - P24C4 : r/Duramax My dad’s 2015 Duramax just threw code P24C4 yesterday. What Does the P21DD Chevrolet Code Mean? The Selective Catalyst Reduction (SCR) system reduces Oxides of Nitrogen (NOx) emissions by injecting a metered amount of Diesel Exhaust Fluid (DEF) or reductant into the exhaust gas stream entering the SCR catalyst. Besides, some other minor electrical component failure can trigger this issue closely connected to the DEF heating system. 6l duramax with codes c0131, p128e and p21dd. What Does the P21DD Chevrolet Code Mean? The Selective Catalyst Reduction (SCR) system reduces Oxides of Nitrogen (NOx) emissions by injecting a metered amount of Diesel Exhaust Fluid (DEF) or reductant into the exhaust gas stream entering the SCR catalyst. 1kpoints) P21DD GMC Code - Reductant Heater 1 Current Too Low. We use cookies to give you the best possible. P21dd p20b9 3500 hd duramax zacatecano1986 492 subscribers Subscribe 66 Share 15K views 5 years ago Check engine light with p21dd and p20b9. There are other helpful videos such as. Diagnostic code P21dd state reductant heater A current to low. What Does the P21DD Code Mean? The Selective Catalyst Reduction (SCR) system reduces Oxides of Nitrogen (NOx) emissions by injecting a metered amount of Diesel Exhaust Fluid (DEF) or reductant into the exhaust gas stream entering the SCR catalyst. P21dd is a code that indicates a problem with the engine’s Duramax turbocharger. P21dd code is set when the GPCM detects insufficient current draw from the reductant tank heater. I just threw this code P21DD (Reductant Tank Heater 1 Low Current) today at 49k miles. My 2014 lml has had three p21dd codes. I did not see any pin damage on my connector when I did the third. My mechanic said the code was P21DD - Reductant Tank Heater and there was a bulletin on it. P21dd is a code that indicates a problem with the engine’s Duramax turbocharger. P21DDI am 37 months and 91K miles, so it looks like it will be outta warranty. The P21DD trouble code on Duramax means “Low Current in the Reduction tank Heater. 2015 Duramax P21DD & P20B9 41,814 views Feb 15, 2018 94 Dislike Share Save Will Brown 132 subscribers Reductant heater replacement. Manufacturers use a heater in the DEF tank to thaw the fluid and allow it to enter the exhaust system, however, this can fail over time. I got an appointment at the dealership next Thursday. Diagnostic code P21dd state reductant heater A current to low. Mechanics Assistant: Just to clarify, whats the exact code? And have you tried to reset it? I have. 7L engine may exhibit an illuminated malfunction indicator lamp (MIL) with diagnostic trouble. If you’re experiencing this code, it’s important to find a mechanic who can diagnose and fix the issue. I talked with a Chevrolet Service writer and discussed what I had discovered from you guys. I went to auto zone and the gave me the code P21DD. I just realized I have the repair manual for the my car as well. Find all the related trouble codes before solving the code P2263. Another def heater problem question : r/Duramax. Discussion Starter · May 20, 2015. I had no issues at the time but a few months later the check engine light came on. Weve started getting colder mornings and its started throwing a P21DD code. 5708899 Inspect the Emission Reduction Fluid Tank electrical connector for any signs of damageand repair as necessary. October 29, 2016 in Technician Corner - Discussions. My 2015 Duramax is throwing P21DD code and P21DDpd code. I took it in and they cleared. You need to remove three Allen bolts. My truck has code P21DD? My name is Nathan, I am hoping to get some insight on what code P21DD means. Truck of my dreams became a nightmare! I custom ordered a $64,000 2011 Chevy 3500 HD crew cab LTZ loaded with a Duramax. Most Common Duramax LML Engine Problems>The 4 Most Common Duramax LML Engine Problems. My 2015 Duramax is throwing P21DD code and P21DDpd code. Diagnostics Pete is online now Related GMC Questions Error code P20B9. Normally a DEF heater failure will cause the CEL to illuminate and a P21DD code to be signaled, but in some cases the CEL will not illuminate. How to repair code P21DD in 2013 Duramax - YouTube 0:00 / 8:52 How to repair code P21DD in 2013 Duramax Master Tech 221 subscribers Subscribe 137 89K views 7 years ago Duramax repair,. 6l duramax with codes c0131, p128e and p21dd. Im guessing you are getting the p21dd code? You should get a long count down and then you will get speed limited to 65 I think then it will keep dropping after so many miles. I have removed the fuel pressure regulator to check for DEF contamination. Last week my def tank froze with a full tank of def, the technical analysis on the code said either water intrusion on the reductant def tank heater wiring harness or a bad def tank heater. Not much online at all regarding the code. P21dd p20b9 3500 hd duramax. Depending on the severity of the problem, it can cost anywhere from $500 to $5,000 to get your engine running properly again. 2014 CTD Error Code P21DD Emission Reductant Tank>2014 CTD Error Code P21DD Emission Reductant Tank. After checking the net and finding you guys. Used scan tool to command heater 1 on-weak. Ill take a look at when i get home this morning for work. My 2014 lml has had three p21dd codes. I send to dealer to resett DEF, they say looks like. My 2014 lml has had three p21dd codes. The glow plug control module (GPCM) shuts off the glow plugs to prevent overheating and reduce fuel flow to the engine. Due to the lack of signal sent from the sensor to the Power Control Module, it happens. P21DDI am 37 months and 91K miles, so it looks like it will be outta warranty. For DTCs P21CD and/or U02A2, this can indicate a concern with connector C4851. Just wondering is this the special warranty I saw on the paperwork when I bought my truck used?. I have a 2014 6. the p128e, I think, sorry I didnt finish typing. If this condition is not found, refer to normal SI. P21dd code can be caused by many factors, such as a disconnected Malfunctioning GPCM,. 6l duramax with codes c0131, p128e …. P21dd is a code that indicates a problem with the engine’s Duramax turbocharger. The auto repair labor rates vary by location, your vehicles make and model, and even your engine type. 2013 Chevy duramax p21DD DEF heater replacement. 5708899 Inspect the Emission Reduction Fluid Tank electrical connector for any signs of damageand repair as necessary. code P21DD Reductant heater replacement on 2015 >How to fix code P21DD Reductant heater replacement on 2015. P21dd code is set when the GPCM detects insufficient current draw from the reductant tank heater. Mechanics Assistant: Are you fixing your vehicle yourself? What have you tried so far?. P161A, I replaced the glow plug…. Had code come up back in December 2015 and paid the dealership to have the whole reservoir replaced at around 65k miles I believe. Duramax P21DD DEF Heater Reservior Replacement TruckNerd 22K views 3 years ago You Have Been Filling Your DEF Tank Wrong Since Day 1: How to Fill Diesel Exhaust. We use cookies to give you the best possible experience on our website. Duramax P21DD DEF Heater Reservior Replacement TruckNerd 22K views 3 years ago You Have Been Filling Your DEF Tank Wrong Since Day 1: How to Fill Diesel Exhaust Fluid Tank ⛽ Thoroughbred Diesel. I put 2 1/2 gallons … read more Keiphun Sowell Owner Brothers Restoratio AutoDiesel Technology 3,289 satisfied customers 2015 duramax that has full Def tank and dash warning wont go 2015 duramax that has full Def tank and dash warning wont go away, any thoughts … read more Robert Blackwell. Error code P21DD - Diesel Place : Chevrolet and GMC Diesel Truck Forums C cmsdock Registered Joined Feb 16, 2014 190 Posts Discussion Starter · #3 · May 2, 2015 wonderful. P2463 and P21DD I’ve been trying to clear the codes while driving so I can do a regen of the dpf system but it keeps going back into reduced power mode Julio Quispe Category: Chevy Satisfied Customers: 3,259 Experience: Automotive Technician at MBR Automotive Ask Your Own Chevy Question Chevy Mechanic: Do you have ability to command functions?. 2015 Duramax P21DD & P20B9 41,814 views Feb 15, 2018 94 Dislike Share Save Will Brown 132 subscribers Reductant heater replacement. My name is Nathan, I am hoping to get some insight on what code P21DD means. PDF TECHNICAL SERVICE BULLETIN 6. Alabama w/ Dreaded P21DD code (DEF heater issue)>Stuck in Alabama w/ Dreaded P21DD code (DEF heater issue). Duramax Fifth Generation: 2011-2016 (LML) Dreaded code p21dd. Manufacturers use a heater in the DEF tank to thaw the fluid and allow it to enter the exhaust system, however, this can fail over time. This is the second time I have received this code since I have owned the truck. com/watch?v=6agMhVPwBvY Steve 2023 Chevy 1500 LTZ 4WD CC 3. I have a 2016 gmc Sierra 2500hd 6. Same code, P21DD. P161A, I replaced the glow plug…>I’m having multiple codes. 2014 Chevy duramax starter replacement. With this being a common issue and having a extended coverage bulletin most dealers keep several on hand (they replace whole tank with updated heater). Error code P21DD - Diesel Place : Chevrolet and GMC Diesel Truck Forums C cmsdock Registered Joined Feb 16, 2014 190 Posts Discussion Starter · #3 · May 2, 2015 wonderful. com/watch?v=pXSSbrZyrLc&t=433s and I feel that if you watch both vid. 6L Im getting a P21DD error code…. ” It mostly happens due to a defect in the reduction tank heater used to heat the DEF. Wouldnt you know, I cleared the code on Sunday and it never showed up again. the truck goes into low power and does not want to start when warm. I say that after watching this video clip: https://www. When I ordered it in December of 2010 there was no mention of a DEF system-none at all. The dreaded P21DD (reductant heater open circuit) reared its ugly head last Saturday. What are the Possible Causes of the Code P262B? Low battery voltage Reprogram Engine Control Module (ECM) Faulty Engine Control Module Engine Control Module harness is open or shorted Engine Control Module circuit poor electrical connection How to Fix the P262B Code? Start by checking the Possible Causes listed above. Napa code reader read P21DD. Just wondering is this the special warranty I saw on the paperwork when I bought my truck used?. 7L engine may exhibit an illuminated malfunction indicator lamp (MIL) with diagnostic trouble codes (DTCs) P21DD, P204C, P21CD and/or U02A2 in the powertrain control module (PCM). Normally a DEF heater failure will cause the CEL to illuminate and a P21DD code to be signaled, but in some cases the CEL will not illuminate. Code P21ddJust called the dealership and he said bring it in Monday to replace the tank. engine may exhibit an illuminated malfunction indicator lamp (MIL) with diagnostic trouble codes (DTCs) P21DD, P204C, P21CD and/or U02A2 in the powertrain control module (PCM). Same code, P21DD. Gen1 Diesel Technical Discussion 2014 CTD Error Code P21DD Emission Reductant Tank Heating System (urea) 212978 Views 181 Replies 59 Participants Last post by Johan Bergen , Oct 23, 2020 C cmsdock Discussion Starter · May 1, 2015 Hey everyone been a while since I have posted here. For DTCs P21CD and/or U02A2, this can indicate a concern with connector C4851. Duramax “upgraded” the injection pump for the LML models, going from the Bosch CP3 to the CP4. I dont understand why the entire tank is being replaced if it is just the heater piece. : 20-NA-195 Cause 5651968 This condition may be caused by a damaged NOx2 sensor, as shown in the graphic. engine may exhibit an illuminated malfunction indicator lamp (MIL) with diagnostic trouble codes (DTCs) P21DD, P204C, P21CD and/or U02A2 in the powertrain control module. My apologies to bump and old thread, but I hope a GM customer satisfaction representative is reading this regarding code P21DD on the 2014 CTD. Code P21DD GMC Reductant Heater 1 Current Too Low. Refer to Workshop Manual (WSM), Section 303-08 and Wiring Diagram, Cell 27. I took it in and they cleared the code. Had I been informed of the DEF being included, I would have gone to another brand. 2K views 3 years ago How to change a. I…>My 2015 Duramax is throwing P21DD code and P21DDpd code. 2013 Chevy duramax p21DD DEF heater replacement - YouTube 0:00 / 14:56 2013 Chevy duramax p21DD DEF heater replacement Bishop’s DIY Auto Repair 321 subscribers Subscribe 2. Stuck in Alabama w/ Dreaded P21DD code (DEF heater issue). How to repair code P21DD in 2013 Duramax. What Does the P21DD Code Mean? The Selective Catalyst Reduction (SCR) system reduces Oxides of Nitrogen (NOx) emissions by injecting a metered amount of Diesel Exhaust Fluid (DEF) or reductant into the exhaust gas stream entering the SCR catalyst. first time was under warranty this time I am afraid it will not be. Oreilly checked it and came up with a P21DD code. It says Hi, I have a 2015 LML Duramax.