2015 Volvo D13 ECU maintenance required

Changed the fuel pressure/temperature sensor which had gotten rid of my stop engine fault issue but I’m still getting the ECU maintenance fault and when I get it I lose a lot of power....is this electrical? Also my truck just clicks and clicks several times before it will start. Are these issues related? Help I’m ready to burn this #####

 

I removed all the bolts used a wire brush got rid of any corrosion, no different. My active fault is P113713 oil thermostat-circuit open....help ‍♀️

 

I lose all power almost like Derate when the fault comes up, sometimes it’ll last 20-30 minutes then go away and I have full power....it comes up while I’m on an incline only

 

Definitely into the cheaper route first and I will check all ground connections when the sun rises in the morning thank you and I’ll be sure to let you know!

 

Really?! Idk this is crazy sometimes it makes no sense! Why would it only be happening up hill when I’m at max load (80,000)? that code on my print out from the dealer said oil thermostat circuit open so possibly a different SA? Idk I’m seriously done with Volvo after this I have 7 payments left and it’s gone!!