i have a 1999 chevy one ton crew cab 4 wheel drive truck. a 454 mtr auto trans. i started having trouble with the speedometer quit working and when i step on the brake both turn signal light in the dash came on. i rebouted the ecm and fixed that, but the speedometer womt worh. it may be the bcm, but i cant find it and i took part of the dah apart. i need help please

Look for the dash ground, sounds like it's loose. I can't remember exactly on that body, some are right under the dash on the drivers side.

Check the dash circuit board for loose resistors. The early 2000s trucks had issues with cold solder joints. i'd imagine a 99 is no different.