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Getting a service message on my exhaust fluid system and is…

Customer Question
Getting a service message...

Getting a service message on my exhaust fluid system and is transitioning to 65mph

Mechanic's Assistant: How many miles are on the car? How has your mileage been lately?

About 87k

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

2015 Denali 2500hd

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

This just happened yesterday. I do not have a dealer within 100 miles

Mechanic's Assistant: Anything else you want the mechanic to know before I connect you?

Don't think so.

Submitted: 9 months ago.Category: GMC
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Answered in 37 minutes by:
11/1/2017
GMC Mechanic: Gabriel Grey, Auto Service Technician replied 9 months ago
Gabriel Grey
Gabriel Grey, Auto Service Technician
Category: GMC
Satisfied Customers: 451
Experience: Master Service Technician
Verified

Good evening, I hope you are doing well. My name is ***** ***** I would be happy to assist you with this.

When the message comes on does it say "Service exhaust system/fluid"? When was the last time the regen procedure was performed?

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Customer reply replied 9 months ago
I added DEF last week. The message says Service on the top and the message is exhaust fluid system. I do not have a dealer within 100 miles of my location. I am down to the 65 limit
GMC Mechanic: Gabriel Grey, Auto Service Technician replied 9 months ago

Ok, it sounds like the unit has developed a hard fault in the system somewhere.

Do you have access to a scan tool so we can see exactly what trouble code it has stored?

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Customer reply replied 9 months ago
No I do not
GMC Mechanic: Gabriel Grey, Auto Service Technician replied 9 months ago

Okay, without knowing the exact code it will be hard to determine exactly what is going on. Usually these develop issues in the def pump/heater assembly, when that happens it will inhibit the regen procedure as well as limit engine speed.

You can try what GM refers to as a Master reset, this may reset the modules long enough to get where you need to go if you plan on taking it somewhere. To perform the reset disconnect both batteries, when the batteries are disconnected touch the positive and negative cables together, this will de-energize the system and put the modules to sleep. In doing so it should clear the warning, if it comes back immediately then it is advisable that you get it taken down to the dealer or somewhere that is Duramax certified to see what exactly is going on with it

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Customer reply replied 9 months ago
Ok I will give that a try tomorrow..
GMC Mechanic: Gabriel Grey, Auto Service Technician replied 9 months ago

Ok awesome, let me know the results

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Customer reply replied 9 months ago
I have the error code. P20B9
GMC Mechanic: Gabriel Grey, Auto Service Technician replied 9 months ago

Ok, that is what I was afraid of. P20B9 is indicative that the DEF heater/pump has developed an open circuit. I have seen a few of these that had the connector back off and cause the issue, but about 90% of the time it has been a failed DEF heater. I would suggest inspecting the connections at the DEF tank to verify that none have come loose. If all connections are good then chances are we are going to need a new heater assembly

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Customer reply replied 9 months ago
Ok will do.
GMC Mechanic: Gabriel Grey, Auto Service Technician replied 9 months ago

Ok great, let me know if you find anything

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GMC Mechanic: Gabriel Grey, Auto Service Technician replied 9 months ago

Hello! Any luck getting this figured out?

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