Cm 2250 power derate question.

[Hammerhead]

Ok, we need to discuss terminology. When you say things without using the correct terminology it really makes it difficult to understand and diagnose.
A) a gauge is in your dash. It reads the signal sent to it in millivolts and displays it in a meaningful way, PSI that you understand.
B) an oil pressure sending unit is the photo I posted in the other thread. It sends a signal, usually in millivolts to the ECM and the gauge that the ECM understands and gauge interprets for you.
What part did you change?
Do you have an Inline connector and Insite software on a laptop?
1)If yes, then learn to use it properly to check, read, repair, and clear the codes.
2)If no, then you cannot clear the code, and the dealer that changed said part should have
3)If the dealer DID clear the code, you still have, or have another issue.
4)If you have not shimmed your oil pump, you should NOT have 55psi of oil pressure, something is wrong