Won't turn over
Replaced the ignition in a 2001 trailblazer turn the
key everything lights up but at full crank it isn't
starting any suggestions
Make sure battery has a full charge and battery connections all good. Note the diagram, check those three fuses, also use a test light and check voltage on those fuses. One fuse is hot all the time, one goes hot with key on, the other goes hot with key in the crank position. Can you unplug starter relay? Sometimes if no terminal numbers at relay in diagram, it may mean the relay is soldered into the fuse box and you can't pull it out, if removeable you could do some testing at the relay. In the old days, we could use a long shank screwdriver and short across the B and S terminal at starter, just to see of starter motor will crank the engine. If you try that make sure tranny is in park or neutral and parking brake is set. Another thought is your neutral switch? I haven't looked at wiring diagram for your security system, to see if starter motor is involved, I don't think it is.
If your saying starter motor won't crank the engine?