Power door lock problems on a 1999 Altima

My wife has a 1999 Nissan Altima. The car has been great since new. However, recently she seems to have a power door lock problem.

She will be driving, etc...with the doors locked, and the relays will start clicking. I know it appears to be a short because it will usually happen after hitting a bump, etc. However, I am not too sure how to begin troubleshooting this.

So far, I bought a Haynes manual that shows the power door lock section in detail. I can see that there are several relays, and something called a Door Lock Control Unit.

Does anyone know where the door relays sit on a 1999?

Does this door lock control unit house the relays internally?

If I am correct, I think this door lock control unit is blue and sits up under the dash.

In the Haynes manual, it says that it is common for wires to break inbetween the body and the door. But the door lock and unlock work everytime from the switches in the drivers door.

Any ideas?????