Two problems related to horn assembly have been reported for the 2006 Chevrolet Trailblazer. The most recently reported issues are listed below.
Horn button in steering wheel becomes progressively more difficult to actuate, eventually failing altogether. Horn can no longer be sounded by pressing on air bag cover on steering wheel. Consequence is inability to sound a hazard warning to other vehicles during an emergency, which can render a collision unavoidable. Defective or misadjusted horn button switch is proven as root cause because horn can still be activated by remote key fob.
Horn doesn't always work. Seems to be a shortage.