One problem related to starter relay has been reported for the 2002 Chevrolet Trailblazer. The most recently reported issues are listed below.
2002 chevy Trailblazer while starting the vehicle, the key has been turned completely in the ignition, a fast, continuous clicking noise will start. (kind of sounds like a detonation device) sounds like it is coming from somewhere in the dash. Relay sensor? overhead lights turn on and off without prompting. While driving, the inside lights flicker on and of. When car is parked and off, inside overhead lights are off - several hours later, return to find inside overhead light(s) on - car was locked. Fast clicking noise is made for several seconds when the air conditioner setting is changed from one setting to another. In example: clicking noise will start when you turn the dial to change from feet and mid body air, to feet air only.