Mercedes Lowers Drops When Parked – Air Suspension – Self Leveling Problems

This week we are troubleshooting a Mercedes-Benz S-Class that lowers itself when parked.  Mercedes-Benz lowering is intermittent.  In some cases, the car will drop itself overnight but not always.  If the vehicle is parked on an incline or downhill, the raising or lowering when parked may stop. There are many possible causes for this malfunction. Mercedes-Benz, with airmatic suspension, tries to self-level when parked, but they end up completely lowering to the ground. In our case, the S-Class would raise to normal height when the car started. The airmatic suspension would normally work for the rest of the trip.

When one level sensor malfunctions or the rod is bent, the vehicle may try to level itself unsuccessfully.  This may cause your Mercedes-Benz to self-level too high or too low.

Symptoms

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Mercedes-Benz E, C, CLK, GL, and S-Class may develop any of the following issues.

• Hissss… air released by the air compressor release valve.
• You hear the air compressor engaging when parked.
• The air compressor releases air when parked.
• Car lowers overnight, but not always.
• Mercedes lowers drops on the rear or front.
• Or Mercedes raises itself when parked.

Cause

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When the car is parked, the airmatic will try to level the car. It does this by discharging air from the airmatic suspension strut that is too high. Typically the car is leveled by lowering the one or two corners of the car that are too high. We also had seen cases when an incorrect installation of the level sensor caused the airmatic to try to level the car by increasing air pressure at a certain strut, raising the car to the maximum setting.

The cause of this problem is usually one of the level sensors. Each of these sensors has two hall effect sensors inside.

• B22/8 Left Front Level Sensor
• B22/9 Right Front Level Sensor
• B22/3 Rear Axle Level Sensor

The two front-level sensors are located at the air suspension struts. Only one sensor at the rear axle will be found in some models. In this case, it measures the position of the torsion bar, which provides an average vehicle height for both rear wheels.

The level sensors measure the current height of the vehicle, and those readings are stored on the airmatic control unit.

You Mercedes-Benz airmatic control unit will calibrate vehicle height. It does this so that one corner of the car is not sitting too low or too high compared to the rest.

When the level sensors are damaged, they can throw off the calibration procedure. The vehicle can’t level itself and releases air via the pressure release valve. Eventually, your Mercedes-Benz lowers to the ground, or it can also raise to the maximum setting.

Possible Misdiagnosis

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A mechanic can misdiagnose vehicle lowering as a leaking air suspension strut or leaking air hoses. This is not always the case. When ONE air suspension (airbag) strut leaks, your Mercedes-Benz will drop significantly on the corner with the leaking air suspension strut.

At the air strut, there are also accelerometers whose main purpose is determining road conditions. If the strut moves up and down too frequently while driving, the airmatic may raise the vehicle as it thinks the road conditions are rough. When the accelerometer fails, they generate fault codes C1123 or C1121. When malfunctioning, they can cause the vehicle to rise to the highest setting.

Solution

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To fix issues such as Mercedes-Benz raises or lowers when parked, you need to start by inspecting the level sensors.

• Inspect the front-level sensors to ensure there is no arm bending. Make sure the wires are not damaged. If you performed any suspension repair, ensure the level sensor at the front airmatic strut is not installed backward.
• Inspect the level sensor at the rear torsion bar. Ensure the connecting rod is not bent.

If the sensors do not have any visible physical damage, your next step is to carry out a vehicle-level calibration. An auto repair shop can perform this, or you can perform it yourself if you have a scanner capable of performing airmatic troubleshooting. You will need a scanner that will allow you to scan multiple control systems in your Mercedes-Benz, including programming, actuating and calibrating sensors.

The YOUCANIC full system diagnostic scanner is a valuable tool for Mercedes-Benz owners who want to troubleshoot problems with their vehicles. This advanced scanner can read and interpret fault codes from the car’s computer system, providing detailed information about any problems with the engine, transmission, brakes, or other critical systems. The scanner can also perform diagnostic tests on various systems, including the ABS, airbag, and steering systems, to help pinpoint the root cause of any issues. With this information, you can make more informed decisions about repairs and maintenance, saving time and money on costly repairs.

In addition to its diagnostic capabilities, the YOUCANIC scanner can help you reset maintenance reminders and service indicators, allowing you to stay on top of your vehicle’s regular maintenance schedule. This is important because regular maintenance is essential for keeping your Mercedes-Benz running smoothly and preventing major problems down the line. Using the YOUCANIC scanner, you can ensure that your vehicle is always in top condition, reducing the risk of breakdowns and other issues that could cause inconvenience or costly repairs. Whether you’re a DIY mechanic or a professional technician, the YOUCANIC full system diagnostic scanner is essential for troubleshooting Mercedes-Benz problems and keeping your vehicle in top condition.

Watch the following video on how to access the airmatic control unit and perform calibration using the Autel DS708 diagnostic scanner.