What is the reason for the BMW 740 reporting an invalid rear axle steering angle signal?
3 Answers
After receiving the vehicle, connect to ISID for diagnostic testing as follows: 480154 - IcM: HSR control module reports a fault; 48f)38c - Rear axle lateral deviation adjustment: motor position sensor value is not credible; 480:388 - Rear axle lateral deviation adjustment actuator: a line fault is identified. This 740Li (parameters and pictures) is equipped with integrated active steering control, which includes Active Steering Control (AL) and Rear Axle Lateral Deviation Adjustment (HSR). The HSR control module is installed in the trunk recess. The HSR controls the servo motor in the rear axle lateral deviation adjustment actuator. A temperature sensor in the HSR control module monitors the final stage of the servo motor. A motor position sensor and a steering tie rod position sensor are installed in the actuator. The signals from these sensors are analyzed by the HSR control module. The HSR control module is connected to FlexRay via the Active Steering Control (AL) control module. The following components are installed in the actuator: servo motor, motor position sensor, steering tie rod position sensor. The electromechanical actuator consists of a servo motor, which moves two steering tie rods through a screw drive mechanism, and the steering tie rods are connected to the follower steering arm.
I've worked on quite a few BMW 740 owners who complain about invalid rear axle steering angle signals, which is quite common. Usually, it's due to issues with the rear wheel steering angle sensor, such as aging internal components or dust accumulation causing signal interruptions; it could also be a software glitch in the control module—BMW's electronic systems occasionally act up; poor wiring contacts or short circuits are also common culprits, as rough roads can loosen connections; or the steering control unit itself might be faulty. Driving with invalid signals can make steering less smooth, and the rear wheels may not respond properly during high-speed turns, significantly increasing safety risks. It's advisable to pull over immediately and check the dashboard warning lights—don't risk continuing to drive. The best approach is to visit a 4S dealership or a professional repair shop to use a diagnostic tool to accurately pinpoint the issue with fault codes. Avoid attempting DIY repairs on complex components to prevent secondary damage.
My BMW 740 had similar issues after a few years of driving. That time when the rear axle steering angle signal became invalid really gave me a scare. It's usually caused by a faulty sensor or poor signal wire contact – BMW's high-tech systems tend to throw errors when unstable. It could also be a bug in the steering control computer requiring a reboot or update; a blown fuse affecting current transmission is another possibility. When this fault occurs, the steering feels uncoordinated, the rear end drags during turns, which is especially dangerous in rainy weather. I immediately drove to the dealership for inspection. The technician said this is a common issue – repairs aren't expensive, but delaying them can make the steering system harder and more costly to fix. I've developed a habit of regularly checking tires and electronic systems, as proper maintenance of luxury cars like BMW can prevent major problems.
