Hello! I just bought a used 2005 prius and noticed the back passenger side door does not lock or respond to locking from the front door lock or the fob. Does anyone know why that is? Is it a fuse or mechanical issue and if it's either, does anyone know where I can get the parts to fix it and hot to fix it?
So the back passenger side door can always be opened from the outside? And this is true even if you directly change the position of the locking knob next to the inside handle on that door? If so, probably the inside door trim needs to be removed for a look-see. The story might be quite simple, but seeing would be the quickest way to know.
The locks made in the late 2000's use a small mechanism that contains a small electric motor which drives some gears that move a rod connected to the lock. There is grease on the gears to minimize wear and make it move smoothly. It's been my experience that the 2002 Prius and the 2010 Camry used similar mechanisms and both had multiple early failures due to the grease becoming stiff. Dried grease keeps the gears from turning. It's not too difficult to replace the mechanisms, but it helps if you have small hands.
The motorized/geared mechanism isn't involved when you directly change the position of the locking knob next to the inside handle on the door, so that would be an easy way to gather info on where the problem might or might not be, before starting to pull off the door trim.
Sadly, that is not correct. The rod from the locking knob goes to a lever on the lock that connects to the linkage on the actuator. When the actuator freezes up the locking rod becomes difficult to move. It will manifest in the "lock knob" being stiff to move and may even bounce back.
In that case, manually working that knob will be an even more revealing test. What I should have said is that most of the motorized/geared mechanism is uninvolved when the knob is moved by hand. The motor typically turns a worm gear, which turns a larger gear that carries a cam. By turning in one direction, it cams the linkage into the locked position, or by turning the other direction, it cams the linkage into the unlocked position. After either operation, it (normally) returns to its central position, where the cam does not interfere with free motion of the linkage in either direction. But that return-to-home isn't done by motor power, but by a spring. If the lock knob turns out to be hard to move by hand, that gives a narrowed-down set of possibilities: either the exact involved lever on the actuator is seized up (probably unlikely), or perhaps the geared mechanism is so gummed with old grease that, after some past use of the electric lock, the spring was never able to return the cam to its neutral position, and now it is in the way of manual actuation. If, alternatively, it is easy to move the lock knob by hand but that doesn't make the door lock, that would leave a different set of possible causes, like a rod that has dropped out of one of its joints. So a quick check with the manual lock knob can tell you a lot. You can also sometimes learn from the sounds made when trying to use the electric lock. When it works normally, in the lock or the unlock direction, you can hear a pretty positive "CHONK" followed by a quieter whirr as it spring-returns. Have to listen pretty closely for the whirr. In total failure cases you may hear nothing. In some intermediate cases, there can be intermediate sounds. A door that's working well can be compared.
