With abs light on you don't have abs. brakes should work as normal/non abs brakes. One note...abs brake systems are often biased to the rear, so if you run w/o abs, the rear often locks first. That's why with abs it's important to hit the brakes hard and hold them...just cuz you feel abs pulse doesn't mean you're at max stop...it's just the abs pulsing the rear brakes!

AFAIK the sensors aren't testable by average guy...but you might want to disconnect the connectors at the front inside the engine compartment and clean them well and reconnect them with a slight dab of conductive grease like OxGard or something. Not too much or it will short the connection.

If that doesn't fix it, it costs about $180 parts and labor to install a new front wheel sensor. Or you can buy one and install it yourself...the big problem is getting the old one out because they're generally corroded in there pretty good and the sensor is destroyed by removing it.