In the XJ6 and earlier (don't know about later cars), there is a pressure sensor which indicates low fluid. When this sensor is bad, or there is air in the line near the sensor, the light will light up when you put your foot on the brakes. Fully bleed the brake system and re-test.
have you checked your brake fluid??
Bring to a shop that has an ABS scanner to determine the problem
Light is usually comes on, when there is a problem with pressure in brake lines. Inspect the brake fluid level, and check for leaks.
When you say the "light on dash" I am assuming your brake warning light. This can be a number of things, not your brake lights. A quick easy check is your fluid level in your master cylinder. A low fluid level will the light come on. When you press your brakes, the fluid level will drop (fluid travelling to the four brakes), when you release the brake fluid is drawn back into the master cylinder. I would check that first.
Is the brake fluid level low in your brake master cylinder in the engine compartment ?
check fluid level
Check your brakes and rotors
I would check switches for faulty sensor on emergency brake...GOOD LUCK
I step on brakes, dashboard light comes on which says stop.
your brake system has air in it and needs bleeding. new calipers are a real hard to bleed
If it comes on when you step on the brake pedal you might need to bleed your brakes. Also check your brake fluid in the master cylinder.
I have noticed that if the brake fluid is low enough in the brake fluid master cylinder it will cause the light to come on when turning left. before it comes on for a low fluid problem because of the fluid shifting.