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Old 08-12-2016, 01:52 PM   #1
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2010 27' FB International
Mechanicsburg , Pennsylvania
Join Date: May 2011
Posts: 6
Duramax (LML) "Service Exhaust Fluid System" Warning

Code P20B9-00

While hitching up last weekend to return home, I started the truck (2012 Silverado 2500HD/Duramax LML) and immediately got this warning message on the Driver Information Center (DIC): "Service Exhaust Fluid System. Check Owners Manual Now".

I was warned that in 99 miles, speed would be restricted to 65 MPH. A countdown was underway to an eventual 4 MPH restriction.

The dealer found Code P20B9-00 for reductant heater/control circuit: when heater #1 was commanded ON, it stayed at .02AMPS. They replaced the DEF heater/emissions reduction fluid tank reservoir...after replacement the amps went to 5.58AMPS.

All covered under the balance of the original factory warranty (I bought the truck used last year). If not for the warranty, the repairs would have cost $1300. Whew!

Just thought I'd pass this along in case anyone else runs into this ominous warning. BTW, the DEF fluid was 75% full when this happened.

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Old 08-12-2016, 04:10 PM   #2
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2012 27' Flying Cloud
W , New England
Join Date: Oct 2012
Posts: 4,664
Duramax (LML) "Service Exhaust Fluid System" Warning

I don't know if I had the same code (2013 Silverado Duramax LTZ) but I had a check engine light and the dealer diagnosed it as a problem with the DEF heater in the tank. Then I found out the vendor who makes the part went out of business! 😳

Thankfully, Amanda - my local dealer service manager - found a tank with the updated part in stock and swapped it out. It too was under warranty.

Sorry I didn't even think to post about it here.

On edit - I too was glad to learn I didn't have to eat the $1300!!
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