2007 Jeep Compass

General Information


Specific to:

Jeep Compass 2007-2009

Jeep Patriot 2007-2009

The Four Wheel Anti-lock Brake System (ABS) is designed to prevent wheel lock-up during braking under virtually any road surface conditions. This allows the driver to retain greater control of the vehicle during braking.

The major components of the system are:

Anti-Lock Brake Module (ABM)
Hydraulic Control Unit (HCU)
Wheel Speed Sensors (WSS)
ABS warning light

The HCU provides 3-channel ABS, or 4-channel with Traction Control, pressure control to the front and rear brakes. The front brake Anti-lock valve provides 2-channel pressure control for the front brakes. Each front wheel brake unit is controlled separately. Two solenoid valves are used in each control channel.

The rear brake Anti-lock valve controls the rear wheel brakes in tandem. The rear brake valve contains 2 solenoid valves.

The front and rear Anti-lock valves contain electrically operated solenoid valves. The solenoid valves modulate brake fluid apply pressure during Anti-lock braking. The valves are operated by the Anti-lock electronic module.

The Anti-lock electrical system is separate from other electrical circuits in the vehicle. A specially programmed electronic control module is used to operate the system components.

The ABS electronic control module monitors wheel speed sensor inputs continuously while the vehicle is in motion. The module will not activate the ABS system as long as sensor inputs indicate normal braking.

Click image to see an enlarged view

Fig. ABS schematic-typical

During normal braking, the master cylinder, power booster, and wheel brake units all function as they would in a vehicle without ABS; the solenoid valves are not activated.

The wheel speed sensors convert wheel speed into electrical signals. These signals are transmitted to the module for processing and determine wheel lock-up and deceleration rate. When a wheel speed sensor signal indicates the onset of a wheel lock-up, the ABS braking is activated.

The Anti-lock system retards the lockup conditions by modulating fluid apply pressure to the wheel brake units. The pressure is modulated according to wheel speed, degree of lock-up, and the rate of deceleration. The solenoid valves are cycled continuously to modulate pressure. The solenoid cycle time in the Anti-lock mode can be measured in milliseconds.