One problem related to brake sensor has been reported for the 2003 Ford Focus. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2003 Ford Focus based on all problems reported for the 2003 Focus.
Brake lockup under abs. When the vehicle is engaged in a braking event sufficient to activate the abs system, all four brakes lockup and do not release until the vehicle has come to a complete stop. This has happened under winter conditions (snow/ice), in the rain and in the dry. The incident in the rain occurred when attempting to take an exit ramp off of an interstate. The car briefly hydroplaned enough for the abs to activate, and then went out of control with the tires locked up. The car slid off of the exit ramp and into the grass, where it finally came to rest. Luckily no one was hurt. The incidents in the dry took place during an auto-cross on a closed course and were sufficient to severely flat-spot the tires. This happens every time abs is engaged under hard braking. Occasionally, it is possible to down-shift and "drive through" the brakes without coming to a complete stop. There is no dash light or anything to indicate a problem. The rear-wheel tone rings have been replaced and the front-wheel tone rings have been cleaned. All four sensors have been cleaned and electrical connections checked for looseness.