Suburban Tail Lamp Brake Lights No Function

High mount light is on a separate circuit, as far as the tail lights need to know if power is getting back to the socket, use a simple test light to check for power.

ok....the parking lamps work, they are in same socket as brake light or do I need to do voltmeter test?

There is a separate wire, (circuit) for brake lights and for tail lights. There is a 3057 bulb in there that is 2 fillemit unless it is just a tail light bulb. Still need to check for power and yes, you can check for 12 VDC instead of a test light.

So if the break lights are not working there is a brake stop relay ether under the dash and or under the hood. Also a brake light switch on the brake pedal arm could be a culpurate

Thanks! I'm going to check it out tonight.