Chevy and GMC Duramax Diesel Forum - View Single Post - 2014 lml p0420 code
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post #16 of (permalink) Old 11-22-2019, 07:43 AM Thread Starter
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Los1wing's Avatar
Join Date: Nov 2019
Location: South Georgia
Posts: 33
99985 miles when the codes first came up. It has been 3000 miles since I've added any def and it still says ok. Maybe I should top it off to see if it is using any.

Most of the trucks life has been on the highway. But this summer I was hauling logs out of the woods. It idled a bit to keep the ac on while I loaded the trailer. Maybe that is how this issue started. I am just now reading that idling is not a good idea.

2014 silverado crew cab 2500 w/t
Manual transfercase
Rollup windows
Stock configuration
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