1999 BMW 323i Brake Pressure Sensor Replacement Cost

Automotive braking systems are responsible for stopping extremely heavy vehicles through the use of hydraulic pressure. Since the braking system must stop such a heavy load, the hydraulic pressure operating the brake system must be extremely high. But what happens when brake pressure starts to decline because of a deficiency in the system? To monitor the brake system operating pressure through the entire range of brake pedal movement, a brake pressure sensor is used to constantly report the amount of brake pressure present in the master cylinder, ABS hydraulic control unit, or individual brake lines at all times. This allows the vehicle's computers to catch a brake pressure failure before it leads to an accident.

The brake pressure switch is installed in direct contact with pressurized brake fluid in the braking system. It is also powered by the battery, ABS control module, or both. The power source is not as important as the signal the sensor sends to the ABS (or other) control module. The signal sent back the the control module will allow the control module to understand how much pressure the brake pressure sensor is subjected to at all times. Since the control module will have a digital map or table of what the pressure should be, when the pressure is outside of the normal range, the brake, traction control, and ABS warning lights will be illuminated. This allows the control module to communicate the error directly to the driver.

There are two scenarios to consider when discussing symptoms of failure for the brake pressure sensor. The brake pressure sensor may fail, but more importantly, the brake system may have a loss in pressure. Understanding the difference is key to diagnosing the vehicle as will be discussed. If the brake pressure sensor reports low brake fluid pressure, the brake, anti lock brake system (ABS), and traction control (TC) lights will illuminate, plus there is the chance of a brake fluid leak. Also, many manufacturers have trademarked names for the TC system, so they will have a different warning light for that system. Some examples would be: ESC, DSC, SH-AWD. However, if the sensor has failed, the reported pressure will be incorrect. The same warning signs will appear, but there is no chance of a brake fluid leak.