A Guide to the 2017-2024 Audi A4 ABS Wheel Speed Sensor
Making sense of dashboard warning lights and choosing the right replacement ABS sensor for your B9 Audi A4.
- A single faulty ABS sensor will disable the ABS, ESC, and traction control systems, causing multiple warning lights.
- Before replacing the sensor, inspect and clean it and the wheel hub area, as dirt and debris can cause the same errors per Audi TSB 2072304/1.
- Replacement is a simple DIY job for most owners, requiring basic tools to access and replace the sensor behind the wheel.
- Quality aftermarket brands like Delphi offer a reliable and cost-effective alternative to more expensive OEM parts.
Understanding the ABS Sensor in Your A4
A faulty ABS wheel speed sensor is a common issue that can cause a surprising number of warning lights to appear on the dashboard of your 2017-2024 Audi A4. While it might look alarming, the problem is usually straightforward. This sensor is a magnet that reads a toothed ring on your wheel hub or axle to determine wheel speed. When it fails, it can't send the correct information to the car's main safety systems.
Symptoms of a Bad ABS Sensor
The most obvious sign of a bad wheel speed sensor is a dashboard that lights up like a Christmas tree. Because the ABS, stability, and traction control systems all use the same data, a single failed sensor will disable all of them. You will almost certainly see the ABS and Electronic Stability Control (ESC/TC) warning lights. You may also see warnings for the electronic parking brake, and Audi's 'Pre Sense' safety system may become restricted.
Check for Debris First
Audi has a Technical Service Bulletin (TSB 2072304/1) for the 2017-2024 A4 that notes an 'implausible signal' from a wheel speed sensor can be caused by dirt, grease, or metallic debris on the sensor tip or the magnetic ring on the wheel bearing. Before buying a new part, it's worth removing the wheel and sensor to inspect and clean the area thoroughly.
🎬 Watch: How to easily check and clean your wheel speed sensors.Choosing the Right Aftermarket Sensor
When it comes to electronic parts on a German car, the choice between Original Equipment (OEM) and aftermarket can be tricky. While an OEM sensor from an Audi dealer offers guaranteed compatibility, a high-quality aftermarket part can provide the same performance for much less money. Here’s a breakdown of the available brands:
- Premium Aftermarket (e.g., Delphi): Brands like Delphi are often OEM suppliers for other car manufacturers and have a strong reputation for quality electronics. For a critical safety component like an ABS sensor, choosing a well-known brand like this is a smart investment.
- Value Aftermarket (e.g., Beck Arnley, Standard Ignition): Beck Arnley is known for often repackaging OEM parts, which can make them a great choice. Standard Ignition (SMP) can be hit-or-miss; while many parts work fine, some users report issues with sensors failing early or being defective out of the box.
Pro Tip: Match the Part Number
Audi uses different sensors for the front and rear axles, and sometimes for the left and right sides. Always confirm the exact part number you need before ordering. The front sensor is commonly part number 4M0927803C, while the rear may be 4M0927807C. Check the part you are removing to be certain.
🎬 See this walkthrough on replacing an Audi A4 wheel speed sensor.Cost of Replacing an Audi A4 ABS Sensor
| Part/Service | Estimated Cost |
|---|---|
| New OEM Sensor | $130 - $160 |
| New Aftermarket Sensor | $48 - $84 |
| Shop Labor | $100 - $200 |
| Total (DIY Aftermarket) | $48 - $84 |
| Total (Shop-Installed Aftermarket) | $148 - $284 |
Frequently Asked Questions
Why are so many warning lights on for just one bad sensor?
Your Audi's Anti-lock Braking System (ABS), Electronic Stability Control (ESC), and Traction Control (TC) all rely on data from the wheel speed sensors to function. When one sensor fails, the computer can't trust the data from any of them, so it disables all related safety systems as a precaution, triggering each system's warning light.
Can I replace just one ABS sensor?
Yes. The sensors fail individually, and you only need to replace the one that has failed. A proper diagnostic scan tool can tell you exactly which wheel sensor is causing the problem (e.g., 'Left Rear Wheel Speed Sensor Implausible Signal').
Do I need to reset the computer after replacing the sensor?
After you replace the sensor, the warning lights on the dashboard may stay on. You will need to use an OBD-II scanner to clear the stored fault codes from the ABS control module. Once the codes are cleared, the lights should go away and stay off.
🎬 Watch: How to use a scanner to reset Audi ABS warning lights.Is the front sensor the same as the rear sensor?
No, they are typically different parts with different part numbers. The front and rear sensors on the B9 A4 are not interchangeable, so make sure you order the correct one for the location you are replacing.
Helpful Videos
Technical Specifications
OEM Part Numbers: 4M0927803C WHT003860B 4M0927807C 4M0927807B
This is an active sensor with a 2-pin connector. The front and rear sensors are different part numbers and are not interchangeable. Always verify the specific part number for your vehicle's axle (front/rear) and potentially side (left/right) before ordering.
We Have This Part in Stock
The information in this article is provided for general reference and educational purposes only. Vehicle specifications, procedures, and part compatibility can vary by production date, trim level, and region. Always consult your vehicle's factory service manual and verify part numbers before purchasing or performing repairs. Safety-critical components such as airbags, seat belts, and braking systems should be installed by a qualified professional.
- Audi A4: