Is "99" A131L trans TCC controlled by the ECU?

[j1999]

Is "99" A131L trans TCC controlled by the ECU?

Trying to troubleshoot surge problem with 1999 Corolla W/three speed A131L trans/AC/No ABS/No cruse control.

While driving on a level surface, if I slowly accelerate with a steady light throttle position, as soon as the car reaches exactly 45 MPH, the car surges by itself. If I then decelerate; say that after the surge the car is now going 55 MPH on the flat and the throttle position remains unchanged, the road then begins to go uphill, as soon as the car slows down to 45 MPH going up the hill, the car will decelerate (power will fall off) by itself.

The car acts as though it has two power bands; low power below 45 MPH and high power above 45 MPH. The driveability is perfect within each of these power band ranges. Only in the transition between the ranges, at 45 MPH does the surge/deceleration occur.

The car can not be driven on a flat at exactly 45 MPH, as by trying to feather the throttle to maintain 45 will cause the car to surge and decelerate quickly (or buck).

There are no error codes in the ECU.

ECU and E2 grounds check OK.

AC on or off makes no difference.

Only happens at 45 MPH, it will do it in both 3rd and 2nd gear.

Car does not surge until it reaches operating temperature.

Only happens with a light throttle position. If accelerating with 1/4 throttle or more, it does not do it, If decelerating with foot completely off gas it does not do it.

I would like to be able to completely rule out a fault with the lock-up torque converter on the A131L three speed transmission in this car. Information I do not have is what controls the TCC lock-up for this transmission? I can only see wires going into this trans for the speed sensor and for the Park/Neutral position switch. Is the TCC in this trans controlled by an internal governor? This could certainly account for the speed link to 45 MPH.

The two theory's I have so far are that the ECU is somehow glitching when it's input from the speed sensor reaches 45 MPH, or that the A131L transmission has an internally controlled TCC lock-up mechanism that is malfunctioning. The fact that the car does not surge until it reaches operating temperature tends to make me think that the ECU is at fault, however it would not be unusual for a transmission to malfunction only when hot.

Any help appreciated.