Hi, I am chasing a loss of rail pressure under load and an associated P1223 code( unknown leak detection based on quantity balance). From my understanding, the ECM sets the P1223 code when calculated fuel flow exceeds an expected value. I/we have checked all the mechanical parts, lift pump, cp3 pump, FCA, PRV, connector tubes, injectors, etc and I still lose rail pressure under load. My question is, are there parameters in a tune that can cause the truck to lose rail pressure. Too aggressive a tune or something along those lines? I am fairly clueless on tuning and trying to get up to speed so I can diagnose this problem. No one can seem to find the problem and I could really use some insight.

Thanks Lebo