No low beam headlights in 04 trailblazer [Archive] - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum

: No low beam headlights in 04 trailblazer

09-14-2007, 02:49 PM
I strarted the truck and realized there were no headlights at night time. Replaced one bulb and no luck. high beams work ok no drl and no low beams at all. Checked all fuese under hood and rear seat. No luck. Any ideas??????????????????????? Please help if you can!!!!!!!!!!!!!!!!!!!!!!!!

09-14-2007, 03:03 PM
If no DRL or Low Beams.....and if all the fuses are okay....then the only thing that you may want to check is the Relays....I believe they are in the fuse box under the hood.......

09-14-2007, 03:12 PM
the ones that are compatible I swapped around and it made no difference but all of them did not have a counterpart.

09-14-2007, 03:14 PM
Looks like you already tried what I was going to suggest - swapping the #45 and #46, the cooling fan and low beam solid state relays.

09-14-2007, 03:22 PM
Check the switch and/or ambient light sensor at the front middle of the dash.

Also make sure the park brake is fully lowered! - Yes, something that simple, the auto headlamps don't come on if the brake is raised even 1 click. (I guess the switch at the park-brake could also be suspect too).

Does everything else on the truck still work? If not, check the back fuse panel and cabling back to the BCM. I believe the headlamps are controlled via the BCM, which sends a signal through the pink/white wire from the gray connector. (Going by memory from the capacitor mod I made to allow the HIDs not to burn out by flickering during the day - TBlazed would know for sure). That pink/white wire should have a voltage signal on it, if the headlamps are being commanded on.....its a PCM (think sine-wave or dashes in morse code) for DRLs.

Brings up a question, do you DRLs work or are they out also?

Update: Just thought of it, a few members have had their wires and/or connectors melt from after market bulbs. Check the bulb connector and wires to make sure they're still healthy. You could also check the voltage on the connector with a meter. If no voltage, use the battery's negative post for ground, to rule out a bad ground wire the the lamp assemblies.

09-14-2007, 03:29 PM
Great` ideas. I tried the ebrake and it appears ok all the way etc. Bulbs have never been replaced till I tried one here recently. I can not manually turn lights on at all with switch and no drl's at all

09-14-2007, 03:30 PM
Also check Fuse #52 the hazard flasher fuse under the hood. I think on 2004 the headlight driver module gets its power from that fuse. Also #53 (i6) the "HDM" fuse if yours has that fuse (#57 with V8).

09-16-2007, 01:29 PM
I must have mixed up the relays once I pulled them as it turned to be the relay for the lows. Any idea where to get one other than the 45 dollar dealer price????

09-16-2007, 03:36 PM
Thanks for checking back in with an update! Another one bit the dust. You are not alone with that failure. That relay seems to be the weak link in the headlight system.

Check with Parts 4 Chevys ( one of TVs vendors for a price. What's the part number on the relay(HDM)? I think it's printed on it.

09-16-2007, 04:04 PM

09-16-2007, 05:15 PM
Here's a 2 year old thread on the subject and what prices were found.

Shop around every TB Envoy etc on the road has two of those relays maybe you could find one (or two one for a spare) in a salvage yard.

09-26-2007, 11:15 AM
My '03 is doing the same thing. Goes off without warning..kinda gets exciting when they do that at 65mph. thanks for the relay tip.

09-27-2007, 10:45 AM
Ok, My 2003 TB has the same problem. I switched the relays and changed the fuses (even though they weren't dead) and the DRL's don't run. I can use the switch to turn on the lights, which is better than before, but I like the auto lights, and that's how the truck is supposed to work. ANYONE got any more ideas? I know I'm gonna forget to turn them off and kill the battery.

09-27-2007, 10:56 AM
Well, I went and put my grill back together and the auto lights work now. Hmmm I think I'll be getting some new relays soon.

Thanks for the post!!

09-27-2007, 11:15 AM
That relay carries a list price or msrp of 34.11 by GM, GMPartsDirect sells it for $20.22, if you need to pick one up. Don't know now some of the dealers can justify selling parts above list, but they do.