HELP!!! 2002 TB will not start

My 2002 Trailblazer just turned 40,000 miles. I went into the garage to start it and it will not start. When I turned the ignition, it seemed like the electical system reset(my clock now reads 12:00). When I try to turn it over, it makes a loud clicking sound from the top center of the engine. I thought it was the starter, but the noise seems to be too high in the engine for this. Any help would be greatly appreciated!

try jumping it.

clicking usually occurs when there is enough juice to run electronics, and get the starter to move, but not turn the engine.

EDIT: Does the engine turn, but not start... or just click and no motion?

When the key is turned, just clicks are heard. The vehicle was just sitting in garage for about 2 hours. It ran and started just fine up to that point.

Just went out this morning and it started up. I think it's time for a new battery since it's almost 5 years old.

When the key is turned, just clicks are heard. The vehicle was just sitting in garage for about 2 hours. It ran and started just fine up to that point.

Just went out this morning and it started up. I think it's time for a new battery since it's almost 5 years old.

Open hood, and remove negitive side battery cable. With negitive cable off, hook up (known good) jumper battery. Retry starting, if engine starts, and runs with jumper in place, remove negitive side of jumper battery. If engine remains running, charging system is OK! Shut off engine and replace old battery. Be on your way.

Could be a battery, dirty battery post or bad battery cable, could be a failing starter or alternator, could be a bad ignition switch. Use extreme caution jumping, adding or swapping batteries as one little arc is all it takes to cook the body control module.

Joel

My '02 TB LTZ just had the same issue. Ran fine one day, wouldn't start the next. I tried a rapid-charge battery jump (60 amp charger), and a jump from my 96 S10. No luck with either one.
So, I took the terminals off the battery, and lo and behold, blue and green crud caked all over both terminals. I cleaned them up real nice and neat and put the battery on a deep cycle. The best charge I could get was about 10 volts. Removed and replaced battery, ops check normal. So far, no issues with any electrical systems on the vehicle.
I just wonder which came first, the corroded posts, or the dead cell in the battery.

Funny...I have a 2004 Trailblazer LT that is doing the same thing. You turn the key and nothing happens, short of some air sounds and a few clicks. Then after a few tries, it would start. I have had it at the dealer twice and it wouldn't do it for them. (sound familiar) Anyway, today it did it in my garage and wouldn't start at all....nothing. Two mechanics came out from the dealer and they say they think the ignition switch is going bad. I hope that's it. That also may be a place for you to start. Hope it helps.