Need help. My 2002 F350 7.3L with 200k loses power under load. Didn't notice problem until I was going up grade with tailer. Speed droped off and everyone was passing me. Engine light came on, but made it home. Analyzer code is P1211. Experienced diesel mechanic did buzz test on injectors and says fuel filters are likley problem. Checked filter on engine, which was clean. What next? Do I clean tank filters?

 

tell us more about the truck..is it tuned?? do you have gauges??did the CEL stay on??how much fuel was in the tank?? how steep is the grade and how much weight on the trailer?? did you notice excessive smoke??

things to check
all the boots on the turbo, if the truck is stock it will defuel @22psi of boost and throw a CEL..
screens in the fuel tank, fuel pump---fuel pressure gauge would be nice..