I have a Lexus is250. I lock my car once and after few seconds after it unlocks. Any reason why it’s doing this?
This is usually because a door is not properly shut, at least that is what happens with my car, done as a warning to you so you don't leave thinking it is locked.
If the doors, hood and trunk are all properly shut then it may be a sensor.
It may also help to have a code reader as, even though there may not be a code, it can tell you the state of all doors etc.