Hi Guys,
I've looked into this as this is becoming a bit of a problem.
For test purposes you set your alarm without the ultrasonics, the alarm will still be active but at least it narrows down the problem.
If you would like to turn to page 168 in the owners handbook it says:
"You can set the security system without activating the ultrasonic sensor. Remove the ignition key, push the lock tab in the drivers door open, then close the door. The security system indicator on the instrument panel comes on for 3 seconds, then starts blinking".
"Even if the ultrasonic sensor is activated or not,the secuirty system can be reset by only the remote transmitter,not the key.
I've also read on the net

that if you unplug the bonnent pin switch the alarm system will not set, the switch is built into the bonnent catch. I have not tried this and not sure if its true, you could always try it!
Hope this helps some of you with cold weather alarm problems.
Mark.