How to pop hood from outside of 2004 chevy trailblazer

Question edited for clarity.
Question moved to model category.

If you get a 4 foot length of 1\4" clear plastic hose, you can put one end in you ear and use it as a stethoscope to track down the humming. The closer you get, the louder the noise will become.

Coolant Flush or engine oil flush?

https://www.google.com/search?q=2004+Chevy+trailblazer+coolant+flush

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You cannot release the bonnet from the outside.

In any case the key should open the driver's door manually. You will need to turn it either once or twice in succession. If it will not open then pull on the handle and turn the key in the lock at the same time.

If it won't close, put some black grease on the latch, drys out.

Your door lock mechanism is wire not rods. That's why door won't open. Need to get power somehow. Look under car and see of you can reach up to the hood latch and release mechanism to open hood. If so open hood and hook up a jumper pack. This should allow you to unlock door.

undewr the hood under the master cylinder..and it can be a bear to change..

under the hood on the passenger side firewall

if it does have a fuse for the trailer lights it will be located in the fuse box under the hood

I would start with the checking the bulbs, fuses, then check the switch.

First face the vehicle so the battery in on the right.
Second open hood.
Third Remove the Grill by pushing firmly on two retainer clips that are on the top, use the wide slot screwdriver to get the rest of the clips off. Pull up gently on the grill it should then pop out. The grill extends under each headlight assembly any other retainer clips should release when the grill in popped out.

Step 2 Fourth on top of the headlight assembly you will see one 1" tab on the right and left side, pull the tabs upward about two inches and this should release the headlight assembly. You then should be able to pull the headlight assembly out toward you.

Step 3 Finally at the back of the headlight assembly you will see two rubber caps one for low beam and one for high beam, the white base is for the low beam and the black base is for the high beam. Unsnap the wire harness from the bulb base, turn the bulb clockwise.

Replace the bulbs high beam on the outside and low beam on the inside.

you have a retaining ring around the socket, on the inside of the hood, you have to turn it, and pull the socket out, do not touch the glass of the new bulb and putting it in, as this will make the bulb explode when it is turned on.