Power Lock Problem

I have a 2001 Camry LE (68K miles) that has an aftermarket alarm system that was installed by the dealer at the time I purchased the car. Recently the lock on the driver's side will not engage. If working normally, when the car is put into gear all locks will engage. This has stopped working. You can hear the lock motor try twice to engage the lock on that side, but it won't work. Also, when I push the lock button on the door, all locks except the driver's side will engage. I have no luck with the remote on the driver's side either (all other doors work fine). When I use the key on that side the lock will engage and I can manually do it as well from the inside.

This happened several months ago, but spontaneously started working again. I can't think of any inciting event that would have made it stop, restart and then stop working again.

Any thoughts? Anything I can try at home (I'm reasonably handy but not a mechanic by any stretch).

Since it is a single door lock issue, your problem lies in the lock actuator in that specific door, so the source of the lock signal doesn't matter. On the 94's that I have it would require the replacement of the door lock/actuator assembly. Yours being a Gen 4 I can't say for sure. But it will require the inner door liner to come off and removal of the unit. Not something for a non mechanic. No offense intended.
Steve

Any idea on cost? It's annoying, but doesn't seem dangerous (as long as I remember to lock the door manually).

I went the the salvage yard and got a doorlock/actuator assy and installed my own so I don't know what you would be charged at a shop to do this.