369 Alarm Valet Mode Problem

Sounds like you need a new alarm siren. Set off the alarm and see if it works then. If not, the rechargeable batteries in the siren have taken a hike, possibly leaking and destroying the circuitry.

 

Behind the trunk back wall, it is removable. There is a vapor barrier as well, you should order one with the alarm siren. It is on the drivers side, about mid way down. 10mm wrench to loosen the nuts, don't remove them, the siren is slotted. A gear wrench works well for this. Unplug and plug in the new one. It will make a loud chirp when you plug it in so be ready for it.
It is not a valet mode, alarm siren battery is just dead.

 

The other problem with the GM unit is that it may trigger the siren whenever the battery disconnect switch is turned off. A few months ago, there was a post describing a method to correct that, but you have to desolder and reprogram an EPROM chip inside the unit.

If you have a US car, no chirping might indicate a bad siren module. If the module is bad, the red alarm LED to the left of the steering wheel will typically stay lit while you are driving.

If your car is Euro, lack of chirps might be normal behavior depending on the original country of destination.

 

I took the corroded battery out and wired in a pack of C cells that equal 7.2V. It charges at 9.6. Works fine now. It does not seem to charge the battery pack with the trickle charger only running the engine. While I was in there I put in an aux alarm that arms the ft bonnet and has a better motion sensor.