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Pete, GMC Technician
Category: GM
Satisfied Customers: 27883
Experience:  14 years GM dealership technician and training.
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My duramax is saying service diesel exhaust system see

Customer Question

My duramax is saying service diesel exhaust system see owners manual now
Submitted: 1 year ago.
Category: GM
Expert:  Pete replied 1 year ago.

Hi my name is ***** ***** I will be happy to assist with this today.In some cases I may need more info to assist better.I apologize for any delay.

What can cause this here is a fault with the DEF fluid being low needing fluid added as in some cases you may not see the low def warning or an issue in some cases with the def fluid freezing (if below 0 degrees in your area).The other issue is a fault with the DEF fluid level sensor or quality sensor.GM has also released a program to correct false DEF warnings as well that should be done by a dealer.

I would start with adding DEF fluid to see if it is low and corrects this here.If it does not and has been below 0 there is a good chance the fluid may have froze in the tank and the truck will need moved to a warmer garage or area to thaw out.I believe this is what the reprogram the dealer does to correct this message if the fluid freezes.

If this is not the issue here then the fault codes will need checked/read out with a scan tool that will plug in and communicate with all computers to see what codes are set.Once this is done any codes set will need diagnosed and repaired to correct this fault here since there are a number of different possibilities for this message to come on having the codes checked is the next step to be done.

If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service.You can rate at any time and we can continue to work on your question as this will not close out your question.Keep in mind in some cases it can be difficult to fully diagnose or help repair your vehicle without seeing it and I work on delivering the best possible answer from what I see to work with.

Thanks Pete

Customer: replied 1 year ago.
Just added fluid five gallons a few days ago. It was written that it can self clear the weather was in the 30's today. I did top it off after which for out that is a not a good idea
Expert:  Pete replied 1 year ago.

If it was a frozen tank issue or low fluid at one point it will clear out but should soon on its own.If it does not then there is an issue with most likely the fluid level sensor or an issue with another sensor like a quality sensor possibly.In this case here you would have to have the codes read out to see what codes are set then those codes diagnosed to locate and repair the fault here.

Thanks Pete

Customer: replied 1 year ago.
Is there a known issue withe the DEF system other than the software update on the Ecm
Expert:  Pete replied 1 year ago.

The only other issues I have seen is a fault with a level sensor or another sensor in the tank like a quality sensor as some have.Usually if this was an exhaust sensor you would have a code for one of the exhaust sensors at fault so the codes do need checked to help locate and repair this issue here.

Let me know if you need anything else and feel free to rate my help here.

Thanks Pete

Customer: replied 1 year ago.
Will do Pete. Do you have access to the schematics for the sensors on the DEF system?
Expert:  Pete replied 1 year ago.

I apologize for the delay as I was offline yesterday.Here are some diagrams I show for this system here.This is the best I was able to get these to show up.If something is there that you need and cannot read let me know and I will check into it for you.

Thanks Pete