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27 December 2025 (updated) Steering Angle Sensor: What It Is, Signs of Failure & How to Test It
Modern vehicles rely on a network of sensors to operate safely and efficiently. One key device is the steering angle sensor (SAS) which helps keep your car stable on the road, especially during sharp turns or emergency manoeuvres, without you realising.
In this article, we’ll explain how it works, how to recognise symptoms of failure, and how it can be tested and recalibrated.
What is a steering angle sensor?
A steering angle sensor measures the direction and position of your steering wheel. It sends this data to the electronic stability control (ESC) system, allowing your vehicle’s computer to calculate how the car should be moving based on steering input.
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If your vehicle starts to skid or swerve, the ESC uses this data to determine whether corrective action, such as braking specific wheels, is needed to bring the vehicle back in line. Without accurate input from the SAS, the stability system can't respond properly, which may compromise handling and safety. Steering angle sensor data is also essential for safety features like lane keeping assist, lane departure warning, and even autonomous driving.
Symptoms of a bad steering angle sensor
When a steering angle sensor begins to fail, the vehicle’s onboard diagnostics usually detect it and trigger a warning light, usually the traction control or ESC light. However, AUTODOC experts highlight that there are several tell-tale signs that may indicate a problem:
- Dashboard warning lights, such as the ABS, traction control, or ESC light.
- Limited power mode: the car may enter a "limp" mode, reducing speed and power.
- Inconsistent steering feel or misalignment.
- Pulling to one side or swerving out of lanes: the control unit may no longer automatically adjust the car’s movement due to faulty readings.
- Squealing tyres while cornering, suggesting incorrect sensor feedback.
- Difficulty with cruise control or lane‑keeping systems, in newer vehicles.
Sensor faults typically appear due to general wear, internal corrosion, or water ingress. Over time, the contact points may deteriorate, causing erratic signals or complete sensor failure. If the car is pulling to one side or there is a loss of steering control, you will also need to check the steering and suspension components themselves, as well as the tyres and wheel alignment.
How to test a steering angle sensor
If you suspect that your steering angle sensor is malfunctioning, testing it with a diagnostic scanner is a reliable at-home method. Here’s a general guide to the process:
- Connect the scan tool to your vehicle’s OBD II port.
- Switch on the ignition and select the SAS module or relevant system in the software menu.
- Calibrate the sensor as instructed. This often involves centring the steering wheel and driving briefly in a straight line.
- Turn the wheel while monitoring the sensor data. Values should change smoothly and proportionally.
- If readings jump erratically or remain static, the sensor is likely faulty.
- Check for stored fault codes relating to the SAS or ESC system for further clues.
This process works similarly whether you’re testing a generic unit or a vehicle-specific part such as a BMW steering angle sensor.
Tip: calibration is especially critical after a wheel alignment, suspension repair, or steering component replacement has been carried out. If in doubt, consult a professional mechanic with advanced diagnostic tools.
When to see a mechanic
Not every SAS fault is straightforward. Sometimes the issue may originate elsewhere, e.g. a wiring fault, a control unit error, or a failing steering system.
You should not forget to look at the car steering rack itself. If your steering feels off-centre or lacks precision, both components should be checked in tandem. A worn rack can cause alignment issues, abnormal sensor readings, or uneven tyre wear.
Replacement & cost considerations
The replacement costs may vary depending on the make and model of your vehicle. Aftermarket units are often available at lower prices, but may require manual calibration. OEM parts may be more costly but are typically pre-programmed for seamless integration.
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If you're comfortable with diagnostics and have access to a scan tool, a replacement and calibration may be done at home. However, because this system is tied to safety-critical functions, many drivers prefer to have the job handled by a certified technician.
Estimated cost ranges (labour + part):
- Basic vehicles: £100–£250
- Premium/luxury vehicles (e.g. BMW, Audi): £250–£500+
- Calibration only (without replacement): £50–£150
Summary
The steering angle sensor is a key player in your car’s safety system, quietly ensuring stability during every drive. If you notice warning lights, odd steering behaviour, or signs of poor handling, it’s worth checking the device with the right tools or with help from a professional.
By understanding its function, failure symptoms, and testing process, you can stay ahead of potential steering issues and keep your vehicle safe on the road.
Frequently Asked Questions (FAQ)
Can I drive with a faulty steering angle sensor (SAS)?
It's not recommended. A malfunctioning sensor may impair your stability control system, increasing the risk of losing control in corners or slippery conditions.
Do I need to recalibrate the sensor after a wheel alignment?
Yes. Even slight adjustments to suspension geometry can affect the SAS’s zero-point. Most alignment services include sensor calibration.
Can the steering angle sensor affect MOT results?
Yes. Dashboard warning lights such as ABS or ESC indicators may cause an MOT failure. A faulty SAS could be the underlying cause.
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