Sustain and Assign functions on Yamaha E403.

[castilrv]

Good day to all.The Sustain and Assign functions on my Yamaha E403 keyboard is not working. I have traced the signals up to the IC802 chip pins and confirmed that the signal levels are ok when the switches are activated. here is the link for the service manual. https://elektrotanya.com/yamaha_psr-e403.pdf/download.html. Thanks in advance.