I had the same problem with the alarm going off straight after the settle period. I checked most of the above but couldn’t get any sense out of the diagnostics. * 17856 * 38 # didn’t result in the LED on the dash flashing, but the keypad LED started flashing after the first few keystrokes. The last trigger isolation code worked in as much as I could arm the system on the first attempt, but then couldn’t get into the car using the key fob. The only way was to use the key barrel where upon I was back to square one as the alarm went off straight away. I have given up trying to fix it, and only lock it with the key barrel now.