My 07 H3 right rear brake light/running light is constantly on, even with all lights off and the key out! The bulb is powered and both filiments lit. It is causing many problems. It eventually blows a fuse called rear turn sig/Hazard number 20. Any ideas? Maybe a short in the BCM pins?

 

sorry, no idea for help. can you remove the lamp or fuse and take it to the dealer? my 07 is still under warranty, yours may be as well.

 

I have an idea. Open the back door, look for the wire harness where it comes from under the chasis, and in part, to the license plate light. There have been many (mine included) that have the harness rubbing on the botton of the door sill opening right where you can see the harness in between the bumber and the truck, if the insulation wears through, you can ground a circuit, open a circuit, and drain your battery. This harness has the rear lights etc.. and trailer power in it.

If the harness is rubbing, inspect it, move it away from contact with the chasis, and re-insulate it separating the wires that are worn.

 

Thanks! I got all excited because I found the exact condition on my H3. Big red wire rubbed all the way threw, green wire also. I could see where it was grounding on the body panel. It was a bear to get to....did the repair...but my right rear tail/brake light is still on.....

 

well i dont know bcm?

shorted wires do not light lightbulbs

shorts blow fuses unless across a switch, unlikley
usually a short is considered to ground

bulbs get lit up by volts supplied by a control like turn signal sw. or brake sw. or light sw

since its one side it sounds like turn signal sw.

that does not explain blown fuse?

i always start by pulling fuses to isolate the circuit

the hummer has a lot of "stuff" in the controls, electronics
etc. lots of stuff to fail

 

It's at the dealer now...actually a Chevy dealer because my Hummer dealer closed...they think its a bad BCM...I will let yuou know. I also have an engine missfire that they can't figure out yet....I will post the results when I get the Hummer back....Thanks!

 

It was a bad BCM...had to wait 3 days for the part, luckily still under warranty. The engine miss-fire code is gone too, they don't know why...I also found the trailer wire harness shorting against the body due to chaffing....seems to be common....maybe I should look into an extended warranty.....