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-   -   P0420 code — Cleaning Exhaust Filter — Unable to solve (https://www.dieselplace.com/forum/63-gm-diesel-engines/365-duramax-fifth-generation-2011-2016-lml/968980-p0420-code-cleaning-exhaust-filter-unable-solve.html)

cnielsen_ 09-04-2018 05:01 PM

P0420 code — Cleaning Exhaust Filter — Unable to solve
 
I am new to this forum. Have not been on any automotive forum in 12+ years so forgive me if this information has been thoroughly covered else where. I drive a 2013 LML LTZ crew cab. 145,000 miles. Second owner. Have owned and driven daily for 3.5 years. Long story short 6 months ago I kept having issues which ultimately resulted in the dealership replacing the entire DPF tank, fluid heater, etc. as the truck had went into limp mode. I should have deleted it then. As of 4 days ago I got a CEL and a message on my display stating “cleaning exhaust filter keep driving until message cleared”. I have read that you must drive and drive somewhere in order for the exhaust filter to clean itself but the specifics of how for, how long, and the perameters have been argued/disputed. The code is P0420 and my reader says “Catalyst System Efficiency Below Threshold (Bank 1)”. So is it the cat or the exhaust filter? Can somebody please offer their best opinion and input on this matter. I am more than eager to delete everything, but still trying to finish paying for another priority at this time.

cnielsen_ 09-05-2018 03:27 PM

Bump — need help!

Joey D 09-05-2018 06:46 PM

I seen a post mention 30 miles or 30 minutes, others chime in just driving in anything but stop and go traffic.

cnielsen_ 09-05-2018 06:53 PM

Drove in excess of 40 miles yesterday on the interstate because I had heard the same thing. The message will disappear off of the display about 5 minutes in. Once you cut the truck off and back on the same message reappears and after a few miles the same Code is thrown.

heymccall 09-05-2018 07:34 PM

The message is unrelated to theDiesel Exhaust Fluid system.
Either the ninth fuel injector is fouled (there's a test for that), or one of the two EGT sensors is slow to respond (there's a test for those, too).

With an experienced Duramax technician, these are easily testable parameters.

rob1 09-05-2018 11:41 PM

Typically this code sets for a failed indirect fuel injector. It can however be a sign of a failing catalytic converter, but it’s highly unlikely. I’ve not seen a case myself of this code coming before one for an EGT sensor if an EGT was failed.

willydmax 09-06-2018 02:14 PM

Quote:

Originally Posted by heymccall (Post 9743222)
The message is unrelated to theDiesel Exhaust Fluid system.
Either the ninth fuel injector is fouled (there's a test for that), or one of the two EGT sensors is slow to respond (there's a test for those, too).

With an experienced Duramax technician, these are easily testable parameters.

I had a 13 LML in the shop with the same code. Ended up replacing the 9th injector and one of the EGT sensors then it finally completed a regen.

mickmosh 09-06-2018 10:30 PM

9th injector just went through this on lml. Same code and i should've deleted...

97chevor 09-06-2018 11:06 PM

I ran in to this issue with fuel additive / bio fuel on my high mileage 2013. Truck would roll white smoke trying to ignite 9th injector. Stopped using addictive in that truck problems went away.

cnielsen_ 09-07-2018 09:07 AM

I appreciate everybody’s input. Huge help. Should I go ahead and replace both EGT sensors, just one(if so which one), or just start with the 9th injector first? None of them look difficult to replace and hopefully clear this issue up while I can save my pennies to delete.


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