Trunk/Liftgate Actuator

This procedure replaces the trunk/liftgate actuator motor that operates the automatic trunk opening and closing system on the 2007-2013 Mercedes-Benz S65 AMG.

Warnings

Tools required

Parts

• Trunk actuator motor assembly × 1 — Mercedes-Benz OEM A2218200342 or equivalent
• Actuator mounting hardware kit (if corroded) × 1 — Use OEM specification
• Trim panel retaining clips (replacement set) × 1 — Use OEM specification

Preparation

1. Park vehicle on level surface and engage parking brake
2. Ensure trunk is fully closed before beginning work
3. Disconnect negative battery terminal and wait 10 minutes for system capacitors to discharge (optional: use memory saver to preserve radio/seat settings)
4. Gather all tools and new actuator assembly
5. Use diagnostic scan tool to document all stored fault codes in SAM control module and trunk systems
6. Open trunk manually using emergency release if needed after battery disconnect

Procedure

1. 1

   Remove trunk interior trim panels
   From inside the trunk, locate the left-side trim panel covering the actuator mechanism. Remove the Torx T20 screws securing the lower trunk side trim panel (typically 4-6 screws). Carefully pull the trim panel away from the body using trim removal tools, releasing the plastic retaining clips. Disconnect any electrical connectors for trunk lighting if present. Set trim panel aside in a safe location.
2. 2

   Access the trunk actuator assembly
   With the side trim removed, locate the trunk actuator motor assembly mounted to the body structure on the left side. The actuator is a black cylindrical unit with a metal pushrod extending toward the trunk lid hinge mechanism. Identify the electrical connector on the actuator body and the mechanical linkage connection at the pushrod end.
3. 3

   Disconnect actuator electrical connector
   Press the locking tab on the actuator electrical connector and carefully pull to disconnect. Inspect the connector pins for corrosion or damage. On S65 AMG models, this connector may have a secondary locking clip that must be released first by sliding it outward with a small flathead screwdriver before pressing the main tab.
4. 4

   Detach actuator pushrod from trunk linkage
   Locate the ball joint or clip connection where the actuator pushrod connects to the trunk hinge linkage mechanism. On most W221 S-Class models, this uses a plastic clip that must be pried off using a small flathead screwdriver. Gently push the actuator rod to compress it slightly, then remove the retaining clip and separate the ball joint from the linkage arm. Note the orientation and position for reinstallation.
   ⚠The actuator pushrod may be under slight spring tension. Control the rod as you disconnect it to prevent sudden movement.
5. 5

   Remove actuator mounting bolts
   Using a 10mm socket, remove the mounting bolts securing the actuator assembly to the body bracket (typically 2-3 bolts). On S65 AMG models, these are usually 10mm bolts torqued to approximately 37 Nm. Support the actuator as you remove the final bolt to prevent it from falling. Carefully extract the actuator from the mounting location, maneuvering it past any obstructing components.
   ℹ️The actuator assembly weighs approximately 3-4 lbs and has an extended pushrod that can catch on surrounding components during removal.
   Torque spec

   Module Mounting Bolts8 Nm (6 lb-ft)
6. 6

   Compare old and new actuators
   Before installation, verify the new actuator matches the old unit in terms of mounting hole positions, connector type, and pushrod length. The pushrod should be in the retracted position on the new actuator. Check that all mounting brackets and hardware are included or transfer from the old unit if reusable and in good condition. Verify the new actuator part number matches Mercedes-Benz specifications for W221 S65 AMG (typically A2218200342 or updated supersession).
7. 7

   Install new actuator assembly
   Position the new actuator into the mounting location, ensuring the pushrod is oriented correctly toward the trunk linkage connection point. Align the mounting holes with the body bracket. Install the mounting bolts hand-tight initially. Once all bolts are started, torque them to specification using a torque wrench. Ensure the actuator body sits flush against the mounting bracket without binding.
   Torque spec

   Module Mounting Bolts8 Nm (6 lb-ft)
8. 8

   Connect actuator pushrod to linkage
   Extend or compress the actuator pushrod as needed to align the ball joint with the trunk hinge linkage arm connection point. Snap the ball joint onto the linkage arm and secure with the retaining clip. Verify the connection is fully seated and the clip is properly locked in place. Gently pull on the connection to confirm it is secure.
9. 9

   Reconnect electrical connector
   Connect the electrical connector to the new actuator, ensuring it clicks fully into place. Verify the secondary locking clip (if equipped) slides into the locked position. Give the connector a gentle tug to confirm secure connection. Check that no wires are pinched or chafing against sharp edges.
10. 10

    Perform initial system test
    Reconnect the vehicle battery negative terminal and torque to specification. Close the trunk manually. Turn the ignition to position II (on) without starting the engine. Use the trunk release button to test actuator operation. The trunk should unlatch and pop up slightly. If the trunk does not operate, check all electrical connections and verify no fuses are blown before proceeding.
    ⚠Initial operation may be erratic or limited until calibration is performed. Do not force the trunk if it does not open or close smoothly.
    Torque spec

    Battery Terminal Bolts6 Nm (4 lb-ft)
11. 11

    Calibrate trunk actuator system
    Connect Mercedes-Benz Star Diagnostic System (SDS) or compatible professional-grade scan tool. Navigate to the SAM control module (Signal Acquisition and Actuation Module) rear section. Select 'Actuators' then 'Trunk Actuator Calibration' or similar function depending on tool interface. Follow the on-screen prompts to perform the calibration procedure, which typically involves opening and closing the trunk through multiple cycles while the system learns travel limits and positions. This step is critical for proper operation and safety.
    ⚠️Ensure all persons and objects are clear of the trunk area during calibration. The trunk will cycle automatically and can exert significant closing force.
12. 12

    Reinstall trunk trim panels
    Position the trunk side trim panel back into place, aligning all mounting points. Reconnect any electrical connectors for trunk lighting. Press the trim panel firmly to engage the plastic retaining clips, working from one end to the other. Install all Torx T20 screws and tighten securely but do not overtighten plastic fasteners.

Reassembly

1. Verify all trim panels are securely fastened with no gaps or rattles
2. Confirm all electrical connectors are properly seated and locked
3. Check that no tools or parts were left in the trunk compartment
4. Clear any diagnostic trouble codes that may have been set during the repair using scan tool
5. Document the actuator replacement in vehicle service records

Verification

• Test trunk operation from all control points: key fob, interior button, exterior trunk release button, and driver's door panel switch
• Verify trunk opens smoothly to full open position and latches in the open state
• Test power close function - trunk should close completely and latch securely without excessive force
• Verify soft-close feature operates correctly (trunk pulls itself fully closed from near-closed position)
• Test obstacle detection - place a soft object (like a foam pool noodle) in the trunk opening path and verify the trunk reverses direction when it contacts the obstacle
• Check that trunk can be manually opened using emergency release from inside trunk compartment
• Verify no warning lights or messages appear on instrument cluster related to trunk system
• Use scan tool to verify no stored fault codes in SAM module or trunk control systems
• Confirm trunk alignment is correct and weatherstripping seals properly when closed
• Test multiple open/close cycles (at least 5) to ensure consistent reliable operation

Related trouble codes on this vehicle

Codes that commonly send this job to the bay — tap one for symptoms, causes, and diagnostic steps.

Chasing one of these codes and not sure which part is guilty? Ask a master mechanic about YOUR car →

More procedures for this vehicle