Pulling the wire at the relay board and pulling the relay just confirm that the DZ input itself does have to be low to trigger this fault, ruling out everything past the COP. Pulling the wire in the COP coming from the mag switch at SRT-13 would have to recreate this fault. Taking the travel cable wire to ground would also pull the input low (or blow the fuse.). If the CLC and the DZ switch have both been replaced, I would want to put my eye balls on every inch of the wire going from the DZ switch splice down to the COP and through every connection to the CLC plug (LCC2). Also pull the LCC2 MTA plug and look in the end of it, use something slightly smaller than the pin to check the spring tension (or just replace it.) I would say park the car at a floor and watch the DZ input at CLC Variable 005 while wiggling plugs but I doubt you would catch it since the FAST response is so slow. The only other thing I can think (besides the possibility of the TC wire grounding) is the diode around the DZ coil on the print. I'm pretty sure that's in the relay, not on the board. Make sure you do successfully recreate the fault though. I am quite confident you can by pulling the wire from the switch or the factory wire from the terminal strip (SRT-13) to the DZ input on the CLC (LCC2-5.) Keep us posted.