1. Faulty ABS Module: The ABS module, also known as the Anti-Lock Brake System control unit, is responsible for monitoring the ABS system and illuminating the ABS light indicator. If the ABS module is defective or malfunctioning, it may not power the light indicator, even when there's a problem with the ABS system.
2. Faulty ABS Wheel Speed Sensor: The ABS system uses wheel speed sensors to detect when a wheel is about to lock up during braking. If one or more wheel speed sensors are damaged, disconnected, or malfunctioning, it can prevent the ABS system from detecting a problem, resulting in the ABS light not illuminating.
3. Faulty Wiring: If there is a problem with the wiring that connects the ABS system to the indicator light or the ABS module, the light may not receive the necessary power or signals to illuminate when needed.
4. Blown Fuse: Some vehicles have a fuse that specifically protects the ABS system. If this fuse is blown, it may prevent the ABS light indicator from coming on. Check your vehicle's owner manual to locate the ABS fuse and inspect it for any damage or blown condition.
5. Software Issue: The ABS system may be controlled by a software program within the vehicle's ECU (Electronic Control Unit). If there's a software glitch or a bug, it may cause the ABS indicator to malfunction or not come on when it should.
It's important to have this issue diagnosed and resolved as soon as possible because a non-functioning ABS system can compromise your vehicle's braking performance and safety. Take your 2004 Toyota Highlander to a trusted mechanic or automotive service center to accurately diagnose the cause and have the ABS system repaired or the indicator light fixed.
