What happens when a Duramax goes to Def?
What happens when a Duramax goes to Def? When it gets to DEF Empty, the message changes to 500 miles to speed 65 mph speed restriction. This is significant, because it doesn't rely on the 'estimate' of how much is in the tank, and how many miles of range it 'thinks' you have until empty. What's the speed limit on a GMC Duramax Def? Click to expand... With my 2018 6.6L I've intentionally taken the the DEF to empty, just to try and verify that it would behave as indicated in the manual. When it gets to DEF Empty, the...