Trick I have used. Isolate your boards. Disconnect the door operator(s)- DOC1 and selector(if you have one)-CSC3. Connect your tool into the SINGLE port in the car station.
- If you gain CLC comm then plug in car top boards one at a time until you reestablish comm with everything or plugging in a particular board causes comm to drop. Replace the board that causes the comm to drop.
- If you don't get CLC comm by isolating it and you have verified power supplies going to the CLC, replace the CLC.