Diagnosis depends on the year, make, and model of the vehicle. If the locking system is controlled by a Body Control Module, a technician will note whether only the liftgate actuator is showing symptoms, or if all of the locks are faulty. If all of the locks are acting the same - failing to lock/unlock, unlocking intermittently, etc. - the BCM may be at fault. The technician will use a scan tool to read data from the BCM. On some older models with a separate lock controller, a software update may be required. If the BCM/controller is functioning properly, the technician will remove the switch inside the vehicle (if so equipped) and test it with a multimeter to make sure it is operating. If the switch has power and is operational, the technician will use the multimeter to check for voltage at the actuator. If the actuator has power but does not function, or if it functions partially, it will need to be replaced.

To replace a liftgate lock actuator, a technician will need to open the liftgate and remove the interior trim panel. Some electrical components mounted in the liftgate may need to be taken out for access. The lock actuator (or the latch assembly in many cases) is disconnected from its linkage and electrical connector.The retaining fasteners are unscrewed and the actuator or latch is removed and a new one installed.

RepairPal recommends that an OEM replacement part be installed in place of a failed liftgate lock actuator. Many aftermarket actuators have a high failure rate. If the actuator prevents the liftgate from locking, as is often the case, no valuables should be left inside the vehicle. Also, the alarm may sound intermittently while the vehicle is locked, so determining the best course of action to protect the vehicle and avoid draining the battery should be taken.

A failing lock actuator can be a symptom of a larger issue with the central locking system, including problems with the BCM or multiple actuators. A fault with the liftgate actuator can cause problems with all of the actuators.

Depending on the specific year, make, and model of vehicle, replacement of the liftgate actuator can be a challenge. The level of challenge depends on whether the actuator is part of the latch assembly or is a separate unit, and how hard it is to access. Vehicle-specific repair information such as an online manual is helpful. An intermediate DIYer can perform the repair in some cases. But, on some vehicles, diagnosis can be difficult if symptoms are related to an electronic problem rather than a single actuator, and a scan tool will be needed.