91 GMC Brake light

I have a problem with my brake light coming on my 91 GMC pickup 4x4. The weird thing is that if I keep the truck below 60 km hr. the brake light will not come on. As soon as I go over 60 km hr. the light will
come on. Could this be the speed sensor causing this problem? Any help would be appreciated.
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Do you mean the light on the dash? if so then yes it could be the speed sensor as this is wired into the RWAL system. Had a similar problem turned out to be the brake light sw. itself, cruise wouldn't work and dash light would come on when you accelerated hard, everything's interconnected in that area. Brake light switch is like 15 bucks and takes about 2 min to change with no tools req.
Good luck :Dave 91 Z71

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