Sorry for posting something about a non-gp..but I have a problem. I have a 1999 GMC Suburban GTS. A couple of days ago I noticed a problem with the lights. When I press the brake all the rear lights go on (including the reverse lights), this also happens when I put on the left signal (brake and reverse lights). Anyone know where I can start with this problem or anyone have any suggestions? THANKS IN ADVANCE!

Have you done any work under your dash lately? I'd first begin by checking for wires that may have rubbed through their insulation and may be grounding out. You might also check the BCM. It controls most of the lighting. The brake light switch could be the culprit too.

Best of luck,
Marc

What is the BCM and where is it?

BCM is short for "Body Control Module". It's the module that stores your settings such as when the doors unlock, how the lighting works in the car,... I don't know where yours would be located, but mine is found below the dash toward the floor by the driver's left foot. It's about the size of a small notebook. The BCM is also the thing that chimes at you when you leave your lights on or keys in the ignition.

Marc