Ok. When you say the self diag system you are talking about when you press the trip reset while turning the key on?
If so, this is telling you if there are codes in just the cluster. If you have none here then I would think the On/Off button are working. Also, you said the cruise light in the dash work correct? If this is the case, then your switches to the servo and the servo to the cluster are working.
If cruise does not set then we need to see if you have voltage on the brake position switch. It looks like the brake pressure switch is used as a back up. According to this attachment the BPP is normally closed to ground so you should have 0 volts on the Tan/Lt Blue wire with the system on and brakes released. When you press the brakes or clutch it should go to 12 volts.
However, due to you saying that the horn pad is the air bag, you may be correct that these switches uses the air bag sliding contacts which is the same thing the horn uses.
So I would suggest testing your brake input to the servo and if that appears to be operating and your indicator in the dash is working then the set/accel buttons are not working because of the contacts.
Thursday, May 2nd, 2019 AT 1:02 PM