Jenn Air Range, replaced sensor and control board/clock, still with F1 code

Jenn Air JDS9860AAP dual fuel downdraft range, serial starts 16… (16 series), bought ~2005. Started giving F1 error code when heated to 450-500F within a minute or two of reaching temp. When ribbon between clock and control board is disconnected, it gives F1-1 error code.

I replaced the temp sensor, problem remained. Then replaced the control board/clock unit, problem remained.

What else is there to do? I was thinking I should test the sensor wiring resistance where it meets the control board but I can’t seem to find a good wiring diagram to know where it connects. Any other thoughts?

Thanks!
Patrick