So I'm in the process of doing a mpg test on my truck on the different octanes and octane tunes. Well today when I switched from 93 octane to 87 octane, my programmer said my truck is throwing 5 codes. 2 of them being U1026 and U1041. NO idea as to what these codes are referencing as they are not in my Haynes book. Kinda clueless on this one.