Pete with Acert derates no code

It depends on the custom file. The ECM could be reacting just as programmed, just not programmed to log a fault. PDI is bad news IMO. A perimeter like coolant temp normally makes gradual fuel adjustments as temp changes, but it could be set to drop a larger percentage of fuel at a certain temp. As far as the ECM is concerned this would be normal operating conditions. It's dumb, but possible, especially with PDI. They are known for preventing the ECM's from logging faults or turning on the warning lights for many problems.

 

I hope you have figured it out by now but nothing is wrong with your engine , to prevent white smoke cat came up with ingenious idea to limit power shut off IVA VVA , oil is thicker can't flow (pressure) in VVA so ECM monitors coolant temp to determine oil temp if ECM detects coolant is too cold so is engine oil it limits power and IVA VVA are not working, once engine reach 167°f engine is normal running , no codes , you cannot turn off Cold Mode , ECM can also stop firing certain cylinders injectors , some after market tuned are without cold mode and those trucks run fine or people live in South doesn't experience this problem. In your case one of the sensor is off or VVA IVa is sticking so it goes upto 200°f When you shut off and restart engine it see water temp is good and derate is gone. Nothing wrong with engine second thing open intake side tubing and look inside head how clean each intake is , is soot deposit powder like or wet like grease , if wet run overhead and see problem solved if no add 3 to 4 cans of Seaform in engine oil (crankcase) close to oil change run 3k-4k miles and it will clean oil deposit it haven't harmed my engine nor viscosity and see if problem solved you feel lot of difference specially in Jakes no vibration even on no1 settings last is find bad IVA VVA housing. But still cold mode will be there and it will run until167°f . Also I run engine on Seafoam filling both filters ( (hot engine)) run 2 min shut off for half an hour and drive , I have incredible results.