Head light Problem with my 2004 Chevrolet Trailblazer 4.2 inline six Repairs for this problem = Replaced both headlight bulbs and checked fuses.
Question = The low beam headlights on my 2004 Chevy Trailblazer dont work. They both went out at the same time. I replaced both bulbs even though I would not think they could go out at the same time. Fuses are all good. What can I do to repair this problem.
Answer: As long as all the fuses are good, and the high beams work correctly, then the common problem is a faulty headlamp relay. This relay is in the under hood fuse block. A lot of the time it is overlooked because it is labeled "HDM". See picture below. This applies to 2003, 2005 and 2006 Trailblazers also.
Most people dont realize this is for the headlamps. An easy way to check that is to swap it with the same type relay that is right next to it. Turn the key off, swap relays, turn key on, then turn head light switch on. It they come on, replace the bad relay. It costs approx. $35.