Need to replace your Mercedes-Benz Air Suspension Control Module? By following the procedures below, learn how to remove and install your air suspension control module.

This guide provides instructions on replacing the air suspension control module (airmatic control unit) or M51 on a Mercedes Benz S-Class W221. Replacing the airmatic control unit on a Mercedes Benz is relatively easy and takes about one hour.


This module was replaced because it displayed a fault code for a faulty air strut ADS valve. The suspension was stuck in SPORT mode, and the ride quality was rough. Even after replacing the “faulty” strut, the code still showed current in the airmatic control module. Wires from the air strut to the airmatic module were tested. Replacing the airmatic module itself fixed the problem.

What you will need

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  • Mercedes Airmatic control unit
  • Used modules can be installed, but ensure you use the correct part number.


  • 10mm socket
  • Ratchet wrench


Follow these steps to replace the airmatic control unit on a Mercedes Benz S-Class W221.


  1. Disconnect the negative terminal on the battery. The battery on W221 is located behind the rear seat and can be accessed via the trunk.
  2. Locate the airmatic control module in the passenger footwell.
  3. Grab one side of the carpet and pull it towards you, and push the carpet down.pull the carpetpull down carpet to max
  4. Remove the 10mm plastic nuts of the module frame, and pull down the metal plate.Plastic nut location 4plastic nut location 2Plastic nut locationPlastic nut
  5. Using a 10mm socket remove the bolts on the metal bracket holding the control module.remove screws
  6. To disconnect the connectors from the control module, you must pull the connector lock and separate the connectors.remove connector


  1.  Align the connectors to the control module and push the tab to lock.Align connector1Align Connector2
  2. Install the metal bracket and tighten the bolts.Return to plate
  3. Return the metal plate, and tighten the plastic nuts.return plate
  4. Install the scanner and program the module.

Even though the module functioned adequately without any programming, transferring the coding from the old control unit is recommended when possible.


  • Make sure to disconnect the battery’s negative terminal every time you perform a module replacement.
  • Make sure to scan the vehicle before performing the module replacement to know what codes are already in store before replacing the module and what occurred after replacing the module.
  • Please back up the coding of the airmatic control module and restore it to the unit.

We hope you find the Mercedes-Benz Air Suspension Control Module Replacement guide helpful. Check these troubleshooting and repair guides for more help on your Mercedes-Benz.

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  1. Hello, great that you have written this guide, but the programming part isn’t detailed. How can I do this at home? I am willing to buy a programming tool if I have to as it is still cheaper than the dealer.

    The ride in my 211 is pretty firm, every expansion joint is very jarring!