Two problems related to back up lights have been reported for the 2002 Chevrolet Trailblazer. The most recently reported issues are listed below.
I have a 2002 Trailblazer with multiple taillight / brake light failures. The dealership has resolved my problem, however I thought this information might be helpful to your open investigation. In November 03 my brake lights failed and my dealership "replaced the bulbs" under my then existing warranty. Again, in January, they failed again and I took the vehicle in to have the "bulbs" replaced. While sitting at the counter, I was speaking to a man behind the parts counter and explaining my problem to him. I hadn't finished explaining when he told me I must have a Trailblazer. I told him yes, and asked him why. He reached under the counter and took out a box with no less than 20 taillight "circuit boards" and told me they were all from Trailblazers.
Brake lights malfunctioned repeatedly/turn signal lights failed three times/headlights, and parking lights also malfunctioned. Vehicle had been in repair shop for these issues at least seven times.