I don’t believe the passlock system sounds the horn.
Hey @Nevada_545
It does on my GMs but I’m pretty sure you have to arm it first. There is a specific sequence for arming as opposed to it not recognizing a key and just disabling starting. Once armed, if a door is opened without the FOB or key, it alarms continuously.
I just ran into this on my TB. I accidentally armed the system and when i opened the door, horn beeping…
@TwinTurbo You are referring to the alarm system, the passkey system is a separate system. The 2005 Classic didn’t come with a factory alarm, I believe it was a fleet vehicle.
This information applies to the 2008 Trailblazer;
Content Theft Deterrent (CTD) Description and Operation
When armed, the content theft deterrent (CTD) system is designed to deter vehicle content theft by pulsing the horns and exterior lamps for approximately 30 seconds when an unauthorized vehicle entry is detected. However, the CTD system does not affect engine starting.
Immobilizer - Passlock System
The Passlock system is provided in order to prevent vehicle theft if the ignition lock cylinder is forced to rotate or the ignition switch is operated while separated from the ignition lock cylinder case. If starting is attempted without authorization, the engine control module/powertrain control module (ECM/PCM) will disable engine starting.
@Nevada_545 You’re right of course. The OP stated earlier on in the thread that the alarm was sounding but did not inhibit starting the engine. This got me thinking about the built in alarm many GMs have but then I mistakenly lumped the CTD and Passlock functions together. Thanks for clarification!