GMC

GMC Troubleshooting Questions? Ask a Mechanic for Answers

Ask an Expert,
Get an Answer ASAP!

GMC

Code p20b9 and code p21dd. Reductant heater and codes P20B(

Customer Question
Code p20b9...

Code p20b9 and code p21dd

Mechanic's Assistant: Just to clarify, what's the exact code? And have you tried to reset it?

Reductant heater and codes P20B( P21DD

Mechanic's Assistant: What is the model/year of your GMC?

P20b9 P21DD 2013 gmc 6.6 diesel 6.6 liter

Mechanic's Assistant: Are you fixing your vehicle yourself? What have you tried so far?

Yes replaced heater kit GM part # 23379348

Submitted: 1 month ago.Category: GMC
Show More
Show Less
Ask Your Own GMC Question
Answered in 1 day by:
1/5/2018
GMC Mechanic: Chris (aka-Moose), GMC Technician replied 1 month ago
Chris (aka-Moose)
Chris (aka-Moose), GMC Technician
Category: GMC
Satisfied Customers: 50,339
Experience: 16 years of experience
Verified

Welcome, I'm Chris (aka-Moose).

  • WORK TIME, I am here 7 days a week but not all hours of the day, do not worry I will respond.
  • FEES, I am a user of the website like you, not an employee. Any fee or account questions need to be addressed to the website.
  • PHONE CALLS are automatically offered by the website. I or another may take the call if you request one.
  • UPLOADED LINKS, if I upload dropbox links, without the phone app use the box on the top right for direct download.
  • RATING ANSWERS, please let me know what you need from me so you are pleased with my answer.

Are you asking for the diagnostic steps for the codes you have?

Ask Your Own GMC Question
GMC Mechanic: Chris (aka-Moose), GMC Technician replied 1 month ago

Hello, Chris here again,

I am checking in to make sure you got everything you expected from my answer. The option to rate my response or reply is still available. I want to make sure you were pleased with what you paid for.

Thanks Chris

Ask Your Own GMC Question
Ask Gm Tech (Cam) Your Own Question
Gm Tech (Cam)
Gm Tech (Cam)
Gm Tech (Cam), GMC Mechanic
Category: GMC
Satisfied Customers: 1,730
1,730 Satisfied Customers
Experience: GM Grand Master Technician 2007. 14 year experience.

Gm Tech (Cam) is online now

A new question is answered every 9 seconds

How JustAnswer works:

  • Ask an ExpertExperts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional AnswerVia email, text message, or notification as you wait on our site. Ask follow up questions if you need to.
  • 100% Satisfaction GuaranteeRate the answer you receive.

JustAnswer in the News:

Ask-a-doc Web sites: If you've got a quick question, you can try to get an answer from sites that say they have various specialists on hand to give quick answers... Justanswer.com.
JustAnswer.com...has seen a spike since October in legal questions from readers about layoffs, unemployment and severance.
Web sites like justanswer.com/legal
...leave nothing to chance.
Traffic on JustAnswer rose 14 percent...and had nearly 400,000 page views in 30 days...inquiries related to stress, high blood pressure, drinking and heart pain jumped 33 percent.
Tory Johnson, GMA Workplace Contributor, discusses work-from-home jobs, such as JustAnswer in which verified Experts answer people’s questions.
I will tell you that...the things you have to go through to be an Expert are quite rigorous.

What Customers are Saying:

Wonderful service, prompt, efficient, and accurate. Couldn't have asked for more. I cannot thank you enough for your help.

Mary C.Freshfield, Liverpool, UK

This expert is wonderful. They truly know what they are talking about, and they actually care about you. They really helped put my nerves at ease. Thank you so much!!!!

AlexLos Angeles, CA

Thank you for all your help. It is nice to know that this service is here for people like myself, who need answers fast and are not sure who to consult.

GPHesperia, CA

I couldn't be more satisfied! This is the site I will always come to when I need a second opinion.

JustinKernersville, NC

Just let me say that this encounter has been entirely professional and most helpful. I liked that I could ask additional questions and get answered in a very short turn around.

EstherWoodstock, NY

Thank you so much for taking your time and knowledge to support my concerns. Not only did you answer my questions, you even took it a step further with replying with more pertinent information I needed to know.

RobinElkton, Maryland

He answered my question promptly and gave me accurate, detailed information. If all of your experts are half as good, you have a great thing going here.

DianeDallas, TX

< Previous | Next >

Meet the Experts:

Gm Tech (Cam)

Gm Tech (Cam)

GMC Mechanic

1,730 satisfied customers

GM Grand Master Technician 2007. 14 year experience.

Gary

Gary

ASE Certified Technician

1,557 satisfied customers

GCM master tech over 25 years

Dave Nova

Dave Nova

GMC Technician

929 satisfied customers

ASE Master Certification. GM World Class Certification

Chris (aka-Moose)

Chris (aka-Moose)

GMC Technician

50,339 satisfied customers

16 years of experience

Ron Z.

Ron Z.

- GMC Tech -

259 satisfied customers

18+yrs experience. State Inspector & GMC Diagnostics/Repair

George H.

George H.

ASE MasterTechnician

227 satisfied customers

15+ Years ASE Master Technician with Level 1 Certification

Don - Mo Lurch

Don - Mo Lurch

ASE Certified Technician

218 satisfied customers

GM, GMC, Chevrolet Cert., Heavy Line Mech, Race Shop Owner, Mobile Electronics

< Previous | Next >

Related GMC Questions
On a 2004 Gmc with a 6.6 diesel it sounds and runs but after
On a 2004 Gmc with a 6.6 diesel it sounds and runs but after it runs awhile it starts loosing oil pressure and knocking… read more
Gm Tech (Cam)
Gm Tech (Cam)
GMC Mechanic
1,730 satisfied customers
My Yukon does not do anything when I turn the key. I took
My Yukon does not do anything when I turn the key. I took battery out and took to auto parts store and it tested good. Took back home. Cleaned up posts and terminals and then it started. Drove to church and now nothing. Any suggestions? … read more
Gary
Gary
ASE Certified Technician
Vocational, Technical or Trade Scho
1,557 satisfied customers
We bought a used 2015 GMC Danall, when sterling either left
We bought a used 2015 GMC Danall, when sterling either left or to right, the vehicle sounds as if something in th3 steering is dragging in addition when the steering reaches its left/right max, it sou… read more
Gm Tech (Cam)
Gm Tech (Cam)
GMC Mechanic
1,730 satisfied customers
What would cause my 2013 2.4 equinox start using oil. Two
what would cause my 2013 2.4 equinox start using oil. … read more
Chris (aka-Moose)
Chris (aka-Moose)
GMC Technician
50,339 satisfied customers
My doors want open from the inside or from the outside? 2008
My doors want open from the inside or from the outside? … read more
Gm Tech (Cam)
Gm Tech (Cam)
GMC Mechanic
1,730 satisfied customers
I have a 2009 GMC Acadia SLT with navigation system and the
I have a 2009 GMC Acadia SLT with navigation system and the CD keeps saying Disc error … read more
Jerry Newton
Jerry Newton
Vocational, Technical or Trade Scho
2,066 satisfied customers
The engine is cranking over but it wont start. replaced all
the engine is cranking over but it wont start. replaced all the spark plugs and wires tonight not getting a spark, replaced the battery and put ether in the engine … read more
Gm Tech (Cam)
Gm Tech (Cam)
GMC Mechanic
1,730 satisfied customers
With regard to the chevy 4L60E transmission for my 1998
With regard to the chevy 4L60E transmission for my 1998 c1500 what does the RCO code mean?… read more
kalamykid
kalamykid
Pactor automotive
Vocational, Technical or Trade Scho
97 satisfied customers
97 gmc, 5.7 L Vortec. I did a serious upgrade to the front
97 gmc, 5.7 L Vortec. I did a serious upgrade to the front of engine, water pump, alternator, timing set, plugs, distributor cap, belts and hoses. the teardown and rebuild took several months and I no… read more
Gm Tech (Cam)
Gm Tech (Cam)
GMC Mechanic
1,730 satisfied customers
I am a DIY. I have a 2016 GMC Sierra C1500 Denali and is in
I am a DIY. I have a 2016 GMC Sierra C1500 Denali and is in flood damage. I am pretty sure most of the electrical modules ECUs need replace/tested. I would like to know what is the best diagnostic equ… read more
Chris (aka-Moose)
Chris (aka-Moose)
GMC Technician
50,339 satisfied customers
Replacing cam sensor. The new one won't go all the way back
Replacing cam sensor. The new one won't go all the way back in. There is a ring inside that is loose … read more
Gm Tech (Cam)
Gm Tech (Cam)
GMC Mechanic
1,730 satisfied customers
I put computer code P1400 cam on. P1400. 2008 Yukon denali.
I put in a computer to diagnose the problem it's showing me code P1400 and P0121 … read more
Dan
Dan
Automotive Technician
Vocational, Technical or Trade Scho
25 satisfied customers
2007 Yukon, replaced blower motor and then resistor, front
2007 Yukon, replaced blower motor and then resistor, front blower worked for a few hours then shut down again? … read more
AMEDEE
AMEDEE
AUTOMOTIVE TECHNICIAN
Vocational, Technical or Trade Scho
9,105 satisfied customers
It was drving fine, but with a check enjine light on for
It was drving fine, but with a check enjine light on for weeks, then just stopped and wouldn't start while doing errands, had it towed home thought maybe the starter, but never had starting issues, ch… read more
Stephen, MBA
Stephen, MBA
Master's Degree
166 satisfied customers
Like to know if install 2 -12 inch high performance fans on
ok like to know if install 2 -12 inch high performance fans on my 1994 gmc SL 2.2 STANDARD PICK UP TRUCK COOLING SYSTEM WILL IT MAKE A DRIFF IN BETTER FUEL AND PERFOMANCE. AND IF YES WHAT IS THE BEST … read more
Mechanic01
Mechanic01
1,988 satisfied customers
Blower motor will only run on high speed. 131000 automatic.
blower motor will only run on high speed JA: How many miles are on the car? Is it an automatic or a manual transmission? Customer: 131000 automatic JA: What is the model/year of your GMC? Customer: 06… read more
TIM MOHR
TIM MOHR
SHOP OWNER
Master's Degree
8,037 satisfied customers
I have a 2002 gmc yukon When i stomp on the gas the car evs
I have a 2002 gmc yukon When i stomp on the gas the car evs up really high but doesnt accelerate I had code p0101 and I changed the MAF … read more
Chris (aka-Moose)
Chris (aka-Moose)
GMC Technician
50,339 satisfied customers
We own a 2015 GMC Yukon Denali. In the last few days the
We own a 2015 GMC Yukon Denali. In the last few days the rear tailgate will open, go all the way up then closes. it does this if we use our foot, hand, or the inside button. … read more
Gm Tech (Cam)
Gm Tech (Cam)
GMC Mechanic
1,730 satisfied customers
Disclaimer: Information in questions, answers, and other posts on this site ("Posts") comes from individual users, not JustAnswer; JustAnswer is not responsible for Posts. Posts are for general information, are not intended to substitute for informed professional advice (medical, legal, veterinary, financial, etc.), or to establish a professional-client relationship. The site and services are provided "as is" with no warranty or representations by JustAnswer regarding the qualifications of Experts. To see what credentials have been verified by a third-party service, please click on the "Verified" symbol in some Experts' profiles. JustAnswer is not intended or designed for EMERGENCY questions which should be directed immediately by telephone or in-person to qualified professionals.

Disclaimer: Information in questions, answers, and other posts on this site ("Posts") comes from individual users, not JustAnswer; JustAnswer is not responsible for Posts. Posts are for general information, are not intended to substitute for informed professional advice (medical, legal, veterinary, financial, etc.), or to establish a professional-client relationship. The site and services are provided "as is" with no warranty or representations by JustAnswer regarding the qualifications of Experts. To see what credentials have been verified by a third-party service, please click on the "Verified" symbol in some Experts' profiles. JustAnswer is not intended or designed for EMERGENCY questions which should be directed immediately by telephone or in-person to qualified professionals.

Show MoreShow Less

Ask Your Question

x