Chevrolet trailblazer 2002 you put the key in the truck won't start and no lights come on?

replace starter motor

Check voltage AT THE STARTER SOLENOID. If there is a good connection at the LARGE connector to the starter solenoid, next check the voltage from the keyswitch to the small wire on the starter solenoid. That's the cylindrical thing attached to the starter. If you have voltage to the small solenoid wire when someone engages the starter at the keyswitch, AND you have a good connection directly from the battery to the Solenoid AND the battery is fully charged and the starter still doesn't engage; you need a starter. On the other hand, if you're not getting voltage to that small wire it could be that you have a problem with the neutral safety switch. Try messing with the shift lever while you hold the keyswitch to the start position. If the starter briefly engages when you do that, it's the safety switch. On the other hand, it could STILL be the safety switch.