5901 / xk01 stopped working after 2 yrs

I installed a viper 5901 and an XK01 bypass in my 2004 trailblazer. All connections were soldered and heat shrinked and it's worked fine for the last couple years. A few weeks back I pulled into work. Hit the arm button and then when I ended my shift and came back out it wouldn't work. No remote start and I had to unlock the truck manually. The most obvious symptom is that the antennae has no power (blinking blue light is gone), and the security light flashes on the dash. The fuse seems to be intact, the XK01 is still showing a steady red light. Given the reputation of the XK01 being flaky I suspect it. But I don't want to spend money unnecessarily. Any thoughts as to what caused this to stop working? Any tips on how to diagnose the problem?

You need to make sure all power connections still have constant power, ground(s) still rock solid and then verify communications from the remote to the brain. I have seen antennas and antenna cables go before. If you are pressing lock and nothing happens, you don't hear any clicking in the brain box then I would lean towards antenna/cable problem. If your wiring checks all good, there is an activation input wire on the viper that you can tap to ground to trigger the remote start sequence. That would let you know that everything wiring wise is working alright for remote start. You can also pulse the doorlock wires to ground and know if the xk01 is still talking to the vehicles databus if it locks the vehicle.Advanced