Well, the good news is you don’t need a new logic board! TCOH is a sensor error for the heat sink per the Apple service manual ‘Excessive processor heatsink temperature.’
'''Review:''' Check CPU heat sink sensor cable connection to logic board. It is located on back side and requires removal of the logic board.
'''Symptom:''' If the sensor is disconnected, the CPU fan will run at full speed.
Here’s the connection point
[image|2053656]