2014 Volvo 670 with Cummins ISX15 won't start

Hi everyone !!! I have a pretty serious problem with my 2014 Volvo 670-70k miles. Truck is still under warranty but as you all know every day of a truck sitting at the dealer is a huge loss for us, and that's why I would like to try to fix it by myself. Since 3 weeks ago I'm having a problem starting a truck. One time it starts right away and another time all the lights on the dashboard lit up like usual and when I'm trying to start it up everything dies-instrument cluster shuts off. I thought that maybe one of the batteries has a bad cell so I replaced all of them but the problem is still there. Then I decided to check the current draw and it turned out to be only 50mA which I think is normal (ecu, clock, radio etc.). Codes that I was able to retrieve are for VECU MID 144 PSID 230 FMI 5 and for Instrument Cluster MID 140 PID 77 FMI 5. One last thing that I need to mention is that when I hoked up the battery charger for few minutes the truck started right away. PLEASE HELP !!! Thanks

 

Will do. Thanks !!!

 

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Seal was where it was supposed to be and all the contacts look brand new

 

When I removed the nut from the master switch I noticed something interesting. The nut got welded to the spring washer and regular washer which I think means that there was a loose connection. View attachment 68663

 

Sorry about that.