What to Do When the Rear Wheel ABS Sensor of a Highlander is Open or Short-Circuited?
2 Answers
The solution for an open or short-circuited rear wheel ABS sensor in a Highlander is to check the wiring connections and reconnect any loose ones. How ABS Works: During braking, the ABS quickly determines the wheel lock-up state based on speed signals from each wheel speed sensor. It closes the normally open input solenoid valve on the wheel that is beginning to lock up, keeping the braking force constant. If the wheel continues to lock up, the normally closed output solenoid valve is opened, causing the braking pressure on that wheel to drop rapidly due to a direct connection to the brake fluid reservoir, preventing the wheel from completely locking up due to excessive braking force. This keeps the braking state at the optimal point (slip ratio S of 20%), ensuring the best braking performance and maximum driving safety. Classification of ABS: ABS is mainly classified based on channels. In ABS, the brake lines that can independently adjust braking pressure are called control channels. ABS systems are divided into four-channel, three-channel, two-channel, and one-channel types. One-Channel ABS: Also known as single-channel ABS, it features a single brake pressure modulator in the rear wheel brake line and a wheel speed sensor installed on the rear axle differential (sometimes one sensor on each rear wheel). Two-Channel ABS: This type of ABS struggles to balance directional stability, steering control, and braking efficiency and is rarely used today. Three-Channel ABS: It independently controls the two front wheels, while the two rear wheels are controlled together based on the low-select principle (i.e., both wheels are controlled by one channel to ensure the wheel with less traction does not lock up), also known as hybrid control. Four-Channel ABS: Equipped with four wheel speed sensors, it has a brake pressure modulator in the line to each wheel brake cylinder, enabling independent control for a four-channel configuration.
I've encountered an ABS sensor open circuit issue before, and it's really annoying. Don't panic yet. First, I'll unplug the sensor connector to check for rust or dirt, then use a multimeter to test if the resistance is within the normal range (normally 5-10 kΩ). An open circuit might mean a broken wire that needs reconnection or splicing; if it's a short circuit, the wire might be touching the car body, so clean and insulate it properly. The rear wheel sensor on a Highlander is located near the brake disc and is prone to getting clogged with mud or having its wiring harness damaged by stones. You can clean it yourself or buy a new sensor to replace it—online parts are cheap and quick, around a hundred bucks. After replacement, make sure to test if the ABS light turns off and if the brakes work smoothly. Safety should always come first—don't skimp on repairs. If the ABS fails due to an open or short circuit, emergency braking could lead to skidding or loss of control, so address the issue as soon as possible.
