I recently just went through the dreaded P20BE Reductant code. I have a 2017 z71 with the 140” box.
Originally I got a notification stating that service emission system 175miles till 65mph max speed. I live in south Texas and this popped up on one of our coldest days at 17 degrees outside temperature, checked the code and there was the P20BE.
First thing I did was research the code on the different forms and saw that a lot of people were having this same issue with reductant heater 2. I drove my truck till the 175 miles was over trying to get the code to go away since it had warmed back up to around 40-50 degrees but wasn’t lucky lol.
Second the display reduced me to 65mph and came up with a new message saying I had 75 miles till max speed of 55mph. At this point I really started doing my research and it seemed that the most common fix was actually replacing the reduction hose to the injector.
Third I was able to borrow a Autel code reader from a friend and started running tests on all the reductant system. I was able to test the def pump in the tank which operated fine, test reductant heater 1 and 2 but it stated there was no current going to either of the heaters once turned on. So this made me think that it could be the control module possibly giving the issue.
Forth I noticed I was showing a malfunction for my NOX sensor 1. This was not shown up as a code but i was able to see that the current going between the NOX and the Oxygen sensors were all malfunctioning. I ended up realizing this was not related to my issue with the P20BE.
Fifth I ordered the parts of RockAuto. Diesel Exhaust Fluid (DEF) Hose ACDELCO DEL 84904154 $105.79. Diesel Exhaust Fluid (DEF) Module GM Genuine 39153712 $138.89.(fyi the Control Module had a Hardware version 9 rather than 8 that was originally on my truck but seemed to have no issue with this).
Finally I got the parted in after about 4 days and installed them both. When I first turned the truck on and checked with the code reader I had 20 codes pop up. After a few key cycles and me clearing the remaining pending codes I was left with 4 permanent codes including the original P20BE. At this point I used the Autel code reader to do the test for the DEF pump and all the codes when away immediately!!!
At this point these 2 parts have seemed to fix the truck and i’m not sure exactly which part it ever was but i’m not complaining compared to the people that have put their vehicle in the shop for a month. I am now dealing with the NOX sensor problem and about to install the new one.
Overall the job was fairly easy to do other than getting the wire connections lose, I’d recommend doing it yourself!
The pictures below are of the DEF Hose with heater 2 on the end with the electric connector, messages on the dash, and malfunctions for the NOX sensor that was not related to the P20BE but is still a issue i’m dealing with.
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