Mercedes GL, GLS, ML, GLE Liftgate Failure (2012-2026): Grinding Noises, Drifting Down, and Software Fixes

Vehicle and Part Compatibility: 166 vs. 167 Platforms

This power liftgate system is used across two distinct generations of Mercedes-Benz SUVs. While the operating principles are similar, the specific part numbers are different. It is critical to match the part number to your vehicle's specific platform and model year.

Common Symptoms of a Failing Power Liftgate Support

Diagnosing a liftgate issue requires paying close attention to the specific sounds and behaviors, as different symptoms point to very different problems.

Grinding or Popping Noises During Operation

A loud grinding, clicking, or popping sound coming from the right (passenger) side of the liftgate is the most definitive sign of failure. This noise indicates that the plastic gears inside the motorized spindle drive have stripped or broken. The motor is trying to work, but the internal mechanism is destroyed. At this point, the only solution is to replace the entire right-side motorized strut assembly.

Liftgate Drifts Down or Won't Stay Open

If the liftgate opens but then slowly drifts downward or slams shut, the problem is almost always the left-side gas support strut. The gas charge inside the strut has leaked out, and it can no longer hold the weight of the heavy tailgate. This is a significant safety hazard, as the tailgate can fall unexpectedly on a person or object. This issue is often more noticeable in cold weather, as the lower temperature reduces the pressure of the remaining gas.

Liftgate Acts Erratically (Reverses, Stops, Won't Latch)

When the liftgate opens part-way and stops, reverses direction unexpectedly, or fails to close completely, the cause is often not the expensive motorized strut. Before assuming the motor is bad, investigate these common causes:

• Failing Left-Side Gas Strut: The control module monitors the effort required to open the gate. If the left gas strut is weak, the motor has to work too hard. The system interprets this extra strain as an obstruction and reverses direction as a safety precaution.
• Software/Normalization Issue: The Tailgate Control Module (TCM) can lose its memory of the proper open and close positions. This is very common after the vehicle's battery has been replaced or has gone dead. Often, a simple reset procedure can fix this without replacing any parts.

Diagnosing the Problem: Motor, Strut, or Software?

Follow these steps to narrow down the cause of your liftgate problem.

1. Listen Carefully: Have a helper operate the liftgate while you stand near the rear. Is there a loud, mechanical grinding noise from the right side? If yes, the motorized strut has failed. If the operation is quiet but erratic, proceed to the next steps.
2. Try a Manual Reset (Normalization): This simple procedure can often resolve software glitches. First, open the tailgate all the way (manually if needed). Then, press and hold the round 'close' button on the edge of the tailgate. Continue holding the button as it closes and for at least 5-10 seconds after it has fully latched, until you hear a beep. This can re-teach the control module the proper limits.
🎬 See how to adjust and set your tailgate opening height.
3. Inspect the Left Gas Strut: Look closely at the metal shaft of the left-side strut. Is there any oily residue? Oil leakage is a sure sign the internal seal has failed and the strut needs replacement. Even without visible leaks, if the gate won't stay open, this strut is the culprit.
🎬 Watch a quick demonstration on replacing the left-side gas struts.
4. Check for Fault Codes: If the simple reset doesn't work, the next step is a professional diagnosis. A Mercedes-specific scan tool can read fault codes from the Tailgate Control Module. Codes like B224E49 or B224555 often point to a software issue that can be fixed by a dealer without replacing parts.

Known Issues, Recalls, and Technical Service Bulletins (TSBs)

• TSB for Fault Code B224E49: Mercedes-Benz issued a TSB for the 166-platform vehicles that addresses this specific fault code. It indicates an internal error in the control module. The official fix is not to replace the module, but for a dealer to perform a software update and re-code it.
• Vehicle Recalls (Not Liftgate Related): While there are no active recalls for the liftgate struts themselves, several recalls exist for these vehicle platforms. These include NHTSA campaign 24V-207 for a loose 48V ground connection under the passenger seat, and 24V-118 for a transmission software issue that could cause stalling. These do not directly affect the liftgate but are important for owners to be aware of.

Buying a Used Liftgate Support: What to Look For

Buying a used OEM part can offer significant savings, but inspection is key. Because the system uses two different types of struts, the inspection criteria are different for each.

Right-Side Motorized Strut (Higher Risk)

This is a complex electronic and mechanical part. Be cautious when purchasing used.

• Source with a Warranty: A recycled OEM part from a reputable seller with a warranty is much safer than a cheap aftermarket clone or a questionable part from an online marketplace. Some used units may have internal electronic faults that prevent them from being programmed to the vehicle.
• Inspect the Connector: Check the electrical connector and its pins. They should be clean, straight, and free of any corrosion or damage.
• Check for Physical Damage: Look for dents in the housing or a bent spindle rod, which could impede its movement.

Left-Side Gas Strut (Lower Risk)

This is a simple mechanical part and is much safer to buy used.

• Check for Leaks: The most important check is for any sign of oil or greasy residue on the polished metal shaft. Any fluid indicates a failed seal, and the strut should be rejected.
• Avoid Physical Damage: Do not buy a strut with significant dents or corrosion on the main black body, as this can compromise the cylinder.

Replacement Overview & Difficulty

The replacement process is generally straightforward for a DIYer with basic tools.

1. Support the Liftgate: Securely prop the tailgate in the fully open position.
2. Access the Struts: On some models, you may need to remove small interior trim pieces near the top of the strut to access the connection point.
3. Disconnect Electrical (Right Side Only): For the motorized strut, locate and disconnect the electrical harness connector.
4. Release the Retaining Clips: The struts are held onto ball studs on the body and tailgate. Use a small flathead screwdriver to gently pry open the metal retaining clip at each end of the strut. You only need to open it slightly to release the tension.
5. Install the New Strut: The new strut simply snaps onto the ball studs. Ensure the clips are secure. Reconnect the electrical plug for the right side.
6. Test and Normalize: Remove the support prop and test the power operation. Perform the manual reset procedure described in the diagnosis section to ensure the system learns the new part's limits.

Cost Comparison: New vs. Used Liftgate Supports

Frequently Asked Questions (FAQ)