yes, the locks get a signal at 15mph (from the speed sensor) and lock. if you cleaned the connection, and it doesnt work, you need to test it, and/or replace it. the sensor is about 50 bucks. chasing the wires, all the way to the ecu, is free for you to do, though. pull apart each connector along the way, and clean out, spray with tuner cleaner, etc.

i'm doing the front abs sensors on my '02 pt cruiser this week. they are bad, and the abs light, brake light and trac light all came on. tested the computer, and it's throwing codes for the front l/r abs sensors. get a scanning tool, and have at it.