2004 BMW 325i Yaw Sensor Replacement Cost

Vehicle stability control is nothing new, but the idea and function of stability control systems are being developed to achieve greater and greater feats. Once component at the heart of stability control systems is the yaw sensor. It measures angular change around the vertical axis of a vehicle. Sounds complicated, but it simply means yaw sensors measure which direction the vehicle is pointing. While it may not be abundantly clear why the vehicle needs to know which direction it is pointing, it all comes into perspective when the vehicle is placed on a roadway - especially around a slippery turn.

Yaw sensors are the next step in a line of components designed to provide next-level performance and handling characteristics to even the most ordinary vehicles. They work in conjunction with the anti lock brake (ABS) and traction control (TC) systems to control wheels individually in order to provide the safest and most recoverable situation for the driver in the event that one or more wheels brakes traction. The yaw sensor measures inertia of the vehicle to determine at which angle the vehicle is turning, and this information is sent to various control modules for further analysis. In a skid, the ABS control module may notice the wheels slipping, and the yaw sensor will report which direction the vehicle is skidding, and these measurements will allow the ABS and TC control modules to take appropriate action to control the skid and recover the vehicle into the intended path. Also, the information from the yaw sensor can be used to prevent sliding or tipping during a turn by requesting the brakes remain locked open or intermittently pressed for individual wheels at specific points throughout the turn.

As soon as any component of the stability control system fails, including the yaw sensor, the driver will receive a message that the stability control system is deactivated, inactive, or off. In many vehicles the TC and ABS lights may illuminate, and any advanced manufacturer specific handling and chassis control system warning lights will illuminate. If the sensor fails to send accurate information, the stability control systems may continue to function for a short while, but they will be deactivated due to unexpected performance when compared to other components of the stability and steering systems. The vehicle should remain generally driveable.

Any time there is a warning light pertaining to the braking system, in this case the ABS light, the vehicle should be brought in for service. Not only do drivers learn to rely on the ABS and TC systems, we become accustomed to these systems unknowingly as we become accustomed to the advanced systems on our vehicles. When these systems are inactive the vehicle can drive and handle dramatically different, again, especially in an emergency situation or inclimate weather. This may be something as simple as accidentally spinning the tires when accelerating from a stop, dragging one or more tires during what seems like normal braking, or as serious as sliding during a turn or tipping the vehicle over. This system will not cause the vehicle to cease function, but if repair cannot be made right away, cautious driving is a must.

Yaw sensors, like all electronic components on modern automobiles, are subject to failure at any time, but typically have a long shelf life. Most vehicles with yaw sensors will be crushed at the end of their service life with the same sensor that was installed at the factory, but there will be some fluke failures. Overall, this is not an alarmingly common repair except with flood vehicles. Flood vehicles will have this sensor, and many more electronic components replaced due to the position of the yaw sensor on most vehicles. They are commonly placed in the center of the vehicle, which means they will likely be on the floorboard below the center console - a common water intrusion area during flooding.

Diagnosis for yaw sensors is slightly complex, at least more so than many electronic components. It can be accurately diagnosed with the use of a professional scan tool, but there is a large margin of error when diagnosing in more traditional ways. The sensor must be read for voltage and angle, and the voltage may seem correct though the angle is not. Also, these sensors need to be recalibrated to 'zero' at some points, so checking for signal values will likely lead to erroneous diagnosis. To identify a failed sensor, the first step is to check for the presence of various control modules related to the system, and also the body control module. If present, diagnostics can move on the the yaw sensor, and the moment and signal value can be checked to ensure they are "at zero" while the vehicle is sitting still. Also, signal values should change proportionately as the vehicle turns.

Accessing the location of the yaw sensor is often complicated due to necessity or removing the center console and possibly seats. Once the location is understood, deconstruction of the interior must be completed before replacing the sensor and returning the interior to original condition. The sensor will be unplugged and removed by extracting a few fasteners or clips, and the new sensor may require calibration upon successful installation.

Yaw sensors should not be reused. Collisions can cause damage to a yaw sensor, so a used yaw sensor from a damaged vehicle may function incorrectly. Also, water damage from a vehicle sitting in a salvage yard can render a yaw sensor useless, and few wrecked vehicles will be kept indoors to prevent loss of components. If the part does not come with a warranty, it is not advised to purchase a used yaw sensor.

As commonly discussed, electronic controls can make diagnostics tricky. This is because a control module can mimic the symptoms of a component that reports to the control module, and the yaw sensor can mimic control module failure. This is not always an issue, but intermittent problems with the yaw sensor will be a difficult diagnosis and may take some time.

This is not a task for the DIY mechanic unless professional diagnostic scan tools are accessible. The computerized testing equipment is too expensive to justify purchase for this issue alone, and the likelihood of the untrained person diagnosing a fault with the yaw sensor. Again, this is a complicated diagnosis, and there is a bit of assumed knowledge involved with these systems and diagnostic tools.