05 lly mpg drop and loss of power

[metz90]

hi everyone i have an lly basicly stock. I was on my way to work one morning and my truck was acting like it wasnt in o/d when driving on the interstate, my first instinct was to remove the bully dog when doing so it made everything worse so i reinstalled the programer and noticed that my mpgs were dropping, nothing big .1 per day or so. i checked my codes and cleared then when i went on a test drive it did not sift into 5 for about 10 miles. once i returned home i like an idiot updated the programer lost my crazy larry tune and now have lost alot of power and when i say alot i mean when on wet pavement wont spin the tires. now its as if its not downsifting or has a slow spool, power level on the programer makes no difference. The dtcs were 0621,0622,0045,0107,0113,0405,2564 please help

 

[JD4440]

How old is the fuel filter? Does it have steering wheel controls so you can check the filter life ?
Here is a DTC list: Pacific Performance Engineering - Diesel Specialists

 

[Dmax-Dualie]

How many miles are on your truck?

I had an issue that was somewhat similar a while back, my truck sometimes wouldnt start unless i primed the filter head and then it would and on others i would be driving normal and have to pass and hit it then it would act like it had no power and wouldnt get over 60 or feel like it had overdrive. When it did downshift while running crappy it again felt like no power.

Turned out to be my filter head was leaking at the o rings, after going to the stealer ship to pick up a rebuild kit they didnt sell one but instead you had to pick up a whole remanned filter head housing for 400+ bucks i told em to sit on it.

I did some looking around and found a store that sells 2 kits plus remanned housings, the kits are a basic for like 15 bucks and an upgraded kit with a billet bleeder screw for 35 or so and the remanned housings for 150. All of it comes with Viton o-rings which are better suited to the ULSD they are forcing on us and dont dry out.

I hope that helps but it may not be your issue, my truck had 135k or so on the clock before this happened. Also ill added what was already stated and check or replace your fuel filter. I talked with Mike L about my trans running wierd about a year ago and he mentioned that if the fuel filter was dirty it would make the trans run funky(how i dont know) and also feel like no power due to the dirty filter of course.

 

[JD4440]

Here's a rebuild kit : Complete Duramax Filter Head Rebuild Kit