How many sensors does the brake pads have for a 2003 Nissan altima?

There are zero brake pad sensors on a 2003 Nissan Altima. Instead, the 2003 Nissan Altima has a visual brake pad wear indicator. This indicator is a small metal tab that is attached to the brake pads. As the brake pads wear, the metal tab will contact the brake rotor and make a squealing noise. This noise is a signal that the brake pads need to be replaced.