check at your brake light switch, its on the frame in front of the brake pedal.
unplug it, and check with a test light or voltmeter. you should have 12v on one of the terminals. if you have 12v on one of the terminals, take a paperclip and jumper it over to the other one. you should then have brake lights...if all is well.
if that checks out ok, you will need to look at the switch, if i recall it is threaded into the bracket. when the brake pedal is depressed, the switch will close (the brake pedal will let the switch release.)
however, if you dont have power on one side, then you have either a blown fuse or an open circuit to it.
hope this helps.
(the lockout solenoid is operated off of the brake switch, btw...

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