Height level sensors

When the height level sensor is faulty, the suspension or stability warning indicator lights may light up on the dashboard. Error messages or specific warnings about the suspension or the body height may also appear. Issues with the vehicle’s suspension may be felt: The vehicle may appear to be lower or higher on one side or at the front or the rear. It may not adjust the suspension correctly, resulting in uncomfortable driving, and the air or adaptive suspension systems may not adjust the body height as intended. Vehicle handling and stability issues may also develop. As a result, the vehicle may become less stable, especially when cornering or at high speed. The vehicle may lean excessively or behave unpredictably when cornering. If the height level sensor is associated with the automatic headlight adjustment system, the headlights may be misaligned, creating a light beam that is too high or too low. The failure of the sensor can also have an impact on driving comfort, with the appearance of vibration or jolting. Faulty sensors can affect stability and traction control systems, reducing their effectiveness. Vehicles fitted with adjustable driving modes may not switch modes correctly, or may deliver sub-optimal performance.

Firstly, we recommend that you visually inspect the height level sensor, in order to determine whether it is faulty. It is therefore strongly recommended that the following components are checked: the sensor itself (for damage, dirt, or debris), the connector (for corrosion and/or loosening), and the wiring (not damaged or broken).

Secondly, you can check that the sensor is working properly using a multimeter, by checking the voltage at the sensor and the continuity of the circuits.

1. Reference voltage: the sensor is receiving the correct reference voltage from the system (often 5 V or 12 V).
2. Output signal: the sensor output signal to see whether it varies according to the body height.

In addition, we recommend that you test the operation of the suspension by raising and lowering it manually (if possible). By doing this, it will be possible to observe whether the suspension reacts correctly to commands. A faulty height level sensor may prevent the correct adjustment of the suspension system.

In the event of force majeure, we will ask you to use an OBD diagnostic tool to identify the fault codes associated with the vehicle height sensor. Specific codes related to the suspension or height level sensors may indicate an issue. For example, codes such as C0711 (Suspension Level Control Sensor Circuit) may indicate issues with the height level sensor.

If the preceding tests are inconclusive, then it would appear that you will need to replace your vehicle’s height level sensor.

Although vehicle sensors meet very strict standards, they do not last forever. A number of factors may result in the need to replace them, including mechanical wear to the arm and the mechanical components. Repeated exposure to environmental factors such as water, humidity, or extreme temperatures can result in failure. Shocks and impacts due to accidents and/or damaged road surfaces can also play a crucial role in the sensor’s service life. In addition, if the vehicle height sensor is contaminated by dirt, debris, or chemicals, then it may be damaged.

We recommend that you follow the steps below to replace your height level sensor as efficiently as possible and to minimize the risk of any error:

1. Disconnect the vehicle battery’s negative terminal.
2. Identify the sensor in question. To do this, it is necessary to use a jack to raise the vehicle, and to install safety stands. The height level sensor is usually located near the axles or wheels.
3. Disconnect the connector. Unscrew the bolts or screws holding the sensor in place.
4. Install the new sensor, refastening the existing bolts or screws.
5. Reposition the connector.
6. Switch on the vehicle and connect the diagnostic tool to check whether there is still an error code. Delete the error code(s) if necessary.
7. Lower the vehicle in complete safety, removing the safety stands and using the jack.
8. Carry out a test drive to check that the new sensor is working properly and that the suspension is adjusting the body height correctly.

As the height level sensor is essential to the correct operation of the vehicle and to driving comfort, it is important to follow certain recommendations in order to prolong its service life:

• Apply the tightening torque recommended by the manufacturers. Otherwise, the injection rail may break or become damaged, or fuel leaks may occur. At Mercedes, for example, the recommended tightening torque is between 8 Nm and 10 Nm, whereas at BMW, it is between 5 Nm and 7 Nm.