Hello guys, I have a 99 lexus gs 300 and the driver side door won’t lock or unlock. I know many people will say it’s the door lock actuator but after many attempts I believe it is something else. My trouble shoot process went like this.. first I purchased door lock actuator from eBay and it did not work. Then I purchased from Amazon, Also did not work. I now decided to rebuild my original actuators and replaced the 10mm rotating motor. I tested the 10mm motors before installing and also tested the actuator before installing and they worked fine. After installation I pressed the remote lock button and also the door lock button and neither of them activated the lock mechanism on the driver door. Every other door worked fine. I find it hard to believe that every single actuator I purchased and repaired didn’t move not one bit. I decided to check fuses on the driver side kick panel and passenger side kick panel and nothing. Is there anything else I should check ? I still need to use multimeter to make sure the wire harness is getting power but is there anything else I can replace that affects the door lock actuator?

 

You may have a faulty driver's door MPX module, which controls the door lock motor.
As a quick test, disconnect the wiring harness from the door module and use a portable 12V DC power supply to apply power to the GREEN-BLACK (negative) and GREEN-RED (positive) wires. Polarity one way or another (lock/unlock). This will let you know where the problem is.