My 996 C2 2001 Cab Tiptronic has always chirped once when locking, telling me there is an open circuit somewhere, but after trying to locate ie radio [afternarket in for 2 years] console, doors, hood and engine for ages just accepted it.
Yesterday when driving the car chirped intermittently for about 10 miles then stopped, the same thing on my return home.
Checked everything nothing has changed, took bumper off yesterday to clean out rads
Checked forum posts and all deal with single chirping when stopped not when moving.

 

What about the cabriolet latch micro switch? Glove box switch?

 

Either buy Durametric or find a friend with it to help solve this mystery. Durametric reads the alarm codes and will pinpoint what is wrong.