Recently going down the road it felt like it was running out of diesel. I had a mechanic recently drop and clean the tank and seems to run low at different levels but frequently around 1/8 tank mark which wasn't quite there but ok. Happened to be right in front of diesel station so whipped in and filled it. Left out and it wouldn't stay running but would start and rev up fine. As soon as in gear it would die out eventually running out of fuel it seemed like. I noticed a puddle near the drivers door where I knew the filter and pump was so after looking the plug on the side was half way loose. Still wondering how that happened but I have replaced that filter 2 weeks prior so I tightened it up but seems like the truck is in limp mode. I have cleared all codes but not sure if you have to clear something special for limp mode. Any help?