Help with a Sony X950

My Sony XBR75X950H TV went out a few weeks ago. Issue was it would begin the start up process but after about 10 seconds it would shut off. Diagnostics output code was 4 red blinking lights.

I have since performed a hard reset and replaced the power board. The first start up with the new power board lasted about 30-40 seconds. Long enough for me to go through some of the first time set up options before it shut down. Another 4 red light code.

I now want to try bypassing the backlight error before replacing all the LED strips. I have found the BLL_ERR wire on the power board but not sure what to do since it goes to the main board and doesn’t go straight to the LED controller.

Any help would be appreciated. I’ve had no luck finding circuit diagrams for this TV online.