2004 Trailblazer LT, 4.2L, L6. Last week my running lights all (front and rear) went out on my truck. Brake, reverse, directionals, hazard all work fine. Switch position does not matter. DTL equipped. Relay swap didn't work. Fuses good. Any input appreciated. Need to fix it before the local constabulary gets wise.

 

By running lights, do you mean your headlights and taillights?

 

Headlights, brake lights, directionals, hazards, backup lights work fine. What we used to call "parking lights" are out...both front and rear. Side markers out. When traveling at night, the truck has no lights showing on rear end unless turning or braking or backing up.

 

You might try checking the fuses and the relay:

 

Thanks. I've seen that video and checked/replaced the relay. All fuses are good; all lamps are good. Everything works except the running/parking lights (front AND rear) and plate lights. This means that, when running at night, there are NO lights at the rear of the truck unless I'm turning, braking, backing up, or have the hazards on. I'm going to wind up with a large fine for improper equipment if I can't find a cure quickly.

 

I have also heard of a flaw in the circuit board itself that is in the taillight housing, but don't know much about it. I'm not in a position right now to do any internet hunting on it.

 

Thanks for the suggestions. All were good but I found the problem: It was a loose wire at the left front parking/running light socket. I found it quite by accident while poking around with a meter. All is well and I avoided a citation for improper equipment. I have no idea how long the lights had been out since I usually drive from inside the truck!

 

Glad you got it going!

 

I am having the exact same problem. Would you be able to describe the location of the loose wire in detail? It was the cause of both rear running lights not functioning properly?

 

No Running Lights - I am having the same issue (no tail-lights - yes on headlights and turn signals), have done all the things listed here and on other web-sights. Fuses, relays, DRL sensor, etal. Have good bulbs and sockets all around (and circuit boards).
SO, a loose wire in a socket may be to blame? Please tell me more! Thanks!