2018 Mercedes-Benz GLS550 Liftgate Pulldown Motor Replacement Cost

Many cars, vans, and SUVs today feature automatic lift gates that make access to the cargo area easy. On some vehicles, the liftgate will raise or lower automatically at the push of a button inside the vehicle or on the key fob. On others, the liftgate must be opened and closed most of the way by hand, but once it contacts the latch, it draws tight on its own, avoiding the need for slamming. These automatic features utilize electric motors to do the work.

The way a liftgate pull down motor functions really depends on the motor involved. There is usually one motor tasked with raising and lowering the liftgate. It is located in the pillar on one side of the liftgate opening and has a moving arm that connects to the liftgate where a liftgate strut might otherwise attach. When the motor receives a signal (most likely from the Body Control Module), it extends or retracts the arm to move the liftgate up and down. Another motor has the job of drawing the liftgate tight once it is closed most of the way. This function can be found with or without the raising/lowering feature. In either case, though, this motor works together with the liftgate latch. It senses when the liftgate striker enters the first stage of the latch and it draws the latch closed the rest of the way automatically. This allows the liftgate to be closed gently, without slamming it closed.

The symptoms of a bad liftgate pull down motor also vary with which each motor. In general, symptoms of a bad motor include a liftgate that will not open and close when the button is pushed, or one that moves at a slower than normal pace. A grinding or whining sound from the pillar on the side of the liftgate opening might indicate a failing motor. If the liftgate is closed partially - where the latch is closed part way - but it does not draw down tight, a motor might be broken. The latch mechanism may make a clicking sound without actually pulling the liftgate shut. There is a difference, though, between a mechanical fault in one of the motors, and an electrical (or electronic) issue with the Body Control Module, a switch, a relay, or the vehicle wiring. Each of these components in the system can be a cause of an inoperative liftgate motor and may lead to some of the same symptoms.

It is important to vehicle safety that the liftgate be able to close properly. If the gate will not close - either automatically or manually - and remain closed, the vehicle should be inspected as soon as possible.

There is no replacement interval for a liftgate pull down motor. These components are supposed to last the lifetime of the vehicle. They do sometimes fail or wear out, and they can become damaged from misuse.

Diagnosis of a faulty liftgate pull down motor depends on the symptoms. If the liftgate will not open and close, or if it is sluggish, if there are strange noises coming from inside the cargo compartment, a technician will suspect a bad motor. Likewise, if the gate will not draw closed, or the latch makes unusual noises, the technician will test the latch mechanism with the gate open to see if it will actuate. If there is no movement of either motor whatsoever, the technician will check for a blown fuse or a bad relay, for the presence of voltage at the motor (and possibly at the switch), and for any fault codes in the Body Control Module.

If the description and diagnosis of each liftgate pull down motor is different, so is the replacement procedure. To change out the motor that raises and lowers a liftgate, a technician will remove the interior trim panels in the cargo compartment on the side where the motor is located. This may require a significant amount of disassembly. Replacement may also require that the technician disconnect the negative terminal from the battery because many vehicles have Supplemental Restraint System components (curtain airbags) located behind the trim panel. With the trim removed for access, the motor wires are traced to the location of the harness connectors and unplugged, the extension arm is disconnected from a supported liftgate, and the motor is unbolted from its mounting location. A new motor is fastened in place and plugged in. The motor that draws the liftgate tight may be mounted to the latch, or it may be integrated into the latch assembly. Either way, the latch must be removed, usually by removing the liftgate interior trim panel, unplugging the latch wire connector, disconnecting any linkage rods or cables, and unbolting the latch assembly. Once outside the vehicle, the latch assembly is either disassembled and fitted with a new pulldown motor, or the entire thing is replaced and installed.

Liftgate pull down motors are included on a vehicle to add convenience. But malfunctions in the system can cause safety concerns. Problems with the function of door latches, locks, and closing mechanisms should be inspected as soon as possible.

Care must be exercised when working around airbags or any other component of the Supplemental Restraint System. Certain vehicle systems may be affected if the battery is disconnected. Also, if the pulldown motor has failed, excessive or otherwise atypical force will be needed to close or open the liftgate, so care should be taken to avoid injury.

Each vehicle with some form of automatic liftgate will present a different set of challenges for a DIYer to work through to diagnose and replace a liftgate pull down motor. The easier of the two types to change will usually be the latch-mounted drawdown motor (usually found in the liftgate). Disassembly can be far more involved if the motor that raises and lowers the liftgate needs to be changed. Intermediate experience is a minimum requirement if a liftgate pull down motor replacement is to be considered.