On early electronically controlled systems with a TCC
solenoid, the clutch is typically applied when oil flow
through the torque converter is reversed. This change can
be observed with a pressure gauge. Connect a pressure
gauge to the fluid line from the transmission to the cooler.
Position the gauge so it is easily seen from the driver's seat.
Then raise the vehicle on a hoist with the drive wheels off
the ground and able to spin freely. Operate the vehicle
until the transmission shifts into high gear. Then
maintain a speed of approximately 55 mph (88 km/h). Once
the speed is maintained, watch the pressure gauge.