Mercedes-Benz vehicles equipped with airmatic suspension have three to four Suspension Height Level Sensors.
Input from these sensors is used by the airmatic suspension to automatically self-level the vehicle height based on the vehicle load. Mercedes level sensors determine the position of the airmatic strut which in turn determines the load of the vehicle. Level sensors are also known as suspension ride height sensor.
A level sensor should not be confused with the axle damping valve unit.
Mercedes Ride Level Sensor Replacement
In the following video, you will learn how to remove and replace the level sensor on Mercedes-Benz with Airmatic suspension.
The work was performed on a W221 S-Class, but the procedure is the same for other models including Mercedes-Benz E-Class, GL-CLass, ML-Glass, CLS-CLass, R-Class and other models with airmatic.
What you will need
A problem that many Mercedes-Benz owners experience is that the linkage of the level sensor breaks or the level sensor itself fails.
When one sensor is faulty, the airmatic system will try to level the vehicle which could lead to a vehicle that is too high or too low.
There is a level sensor for each of the front two air struts. A third level sensor is often located above the rear axle (near the rear differential) attached to the rear sway bar.
The third suspension level sensors measure the approximate position of the two back air struts. If this level sensor fails or the linkage breaks, the vehicle will drop on the back (both sides).
If one of the suspension height level sensors fails, you will notice one or more of the following symptoms.
- Airmatic Malfunction Visit Workshop message on the instrument cluster
- Stop Car To Low message
- Vehicle drops to the ground at one of the front corners.
- The strut is locked out at full inflation and very high
- The back of the car (both sides) drops to the ground
if the rear axle sensor fails. The rear of the car will
not raise even with new struts.
- Airmatic - Visit Workshop Displayed in Instrument
cluster and Fault Code 5151 - [B22/3 (Rear Axle Level
Sensor): Signal Implausible]
Troubleshooting Mercedes Level Sensor
Often when a Mercedes is taken in for another service such as a control arm or air strut replacement, the mechanic working on the car accidently bends the B22/9 or B22/8 sensor mounting plate or the linkage.
In turn, the airmatic control module no longer reads the correct vehicle heights.
We recommend that first, you should check the level sensor link, wiring and mounting place. From our experience, it is more common for the link to bend or fail than the level sensor.
The link itself can often break causing the level sensor to malfunction.
If you are experiencing problems with the airmatic always start by checking the ride height level sensor links.
Remove the front two wheels and inspect the suspension level sensor mounted next to the upper control arm.
You have a level sensors at each front strut. Depending on chassis, you will have a level sensor above the rear axle or one for each rear strut.
If you notice that the linkage is bend, you can just bend the sensor back to the correct position.
The problem is that in many cases the link is either rusted or damaged beyond repair. If that is the case we recommend that you replace a faulty level sensor with an OEM Mercedes Level Sensor.
If the link is not damaged, the next step is to read the fault codes using an OBDII scanner that is designed for Mercedes-Benz vehicles.
Mercedes Level Sensor Location
Description of Ride Height Level Sensors on vehicles with three sensors. Vehicles with four sensors have one sensor at each air strut.
- B22/8 Left the front level sensor
- B22/9 Right front level sensor
- B22/3 Rear axle level sensor
You can purchase replacement Mercedes level sensors online. Search for Mercedes Ride Height Sensor for your model.