Anti-Lock Brake System (ABS) Warning Indicator
WARNING: This page is about a different car, the 2005 Ford RV Cutaway, 2005 Ford Econoline, and 2005 Ford E450 Super Duty. However, it is still accessible from the selected car via links, so may be relevant.
The instrument cluster receives status information from the ABS module through a hardwired circuit from the ABS module. During normal operation, the ABS module supplies a ground to the ABS warning LED circuit, shutting the LED off. If the ABS module detects a fault, or if the ABS module is disconnected, ground is removed from the circuit, causing the ABS warning indicator to illuminate.