2004 GMC Canyon SL 5 Cyl 3.50L
brake lights will not light up but when i turn on headlight tail lights come on , what is wrong?
May be the brake light switch beneath the brake pedal is faulty. First, check the connection (plug) and wiring for proper connection / looseness at the switch. Also, check the fuses and relays for corrosion and proper contact within the individual holder.