Two man job ... Have someone build and hold pressure on the pedal while watching the warning light.
Second person cracks open a bleeder on the opposite end, front or rear, of where you think the valve has shifted to, until the light goes out.
One person job, (the only way I've done it, usually work by myself) ... Open a bleeder, cross your fingers, and stab the pedal once. Tighten bleeder.
Its always worked for me, if the block is functioning correctly.