Just a quick update on my progress
After 3 months of off and on troubleshooting due to a shoulder injury, I got no where still. I checked the tail lamp circuitry and everything looks ok. Terminal 21 of IDPM is energized. I pulled the IPDM and bench tested it again, everything seems fine. I went ahead and re-solder all the solder joints in the IPDM just in case there was a cold solder joint some where. Plugged everything back in the problem came back after 15 minutes driving.
I used a stethoscope to help identifying the location(s) where the clicking sounds come from when the instrument panel switched off and on and the sounds seem to come from behind the fuse block by the parking brake pedal. FSM PG-12 showed there are two relays (Accessory and Blower relays) are mounted on the back of the fuse block but I couldn't figure out how to remove the fuse block to check the relays.
After spending more time reading FSM PG, it looks like the coils for both relays are fed by the PDU; that might explains the clicking sound when the instrument panel turned off and on. I tried to follow the schematics but I got lost since I don't know where to find the PDU in my car. Is it the same as the IPDM? What are M31, M16, and M70? My thinking is there is either a lose connection on M31 or the ground is my problem since when the instrument panel turned off, the blower fan, the AV control screen are also turned off. Please let me know if you have any suggestions on how I should continue with my troubleshooting. BTW, I thought maybe my battery is weak even though I had it tested out good so I went ahead and installed a brand new higher CCA battery since then but the issue remains the same.
Thank you in advance for any help you can provide.