It's an 2001. Lock and unlock is at the slower speeds, less than 47 MPH. Let up on accelator and it unlocks, give it accelerator and it locks.
When above 47 MPH, it unlocks when it start to pull, not too heavy. The engine will simply not lug down and let the RPM's decrease with MPH.
Perhaps unfair to compare to my 96, but the converter locks at about 30 MPH and will stay locked even after shift to OD. It stays locked until manually released or I can lug engine down to near 50 MPH before auto unlock. Maybe this is the differance between the old manual fuel control and the newer electronic.
sounds like there might be an issue with it it should stay locked more often if under 47 and it engages and disengages alot without alot of pedal movement have seen corroded battery cables at the ends cause this even at higher speeds... the alt is trying to charge the system and gets spikes in the system giving the throttle position sensor skewed voltages and the pcm sees these as pedal movement... take a look there otherwise i would have someone look at it with a scanner possibly do a converter clutch test... try that