A couple links to help you...
http://www.supramania.com/forums/showthread.php?t=111721
http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=FA&P=29
Probably the first thing you should do is check to make sure the TEMS system is even engaging. To do this, with the car off, turn the key to the "ON" position without starting the car, then cycle through the buttons on the TEMS controller. If TEMS is working as it should, you will hear an audible "click" after selecting between NORMAL and SPORT modes. If you do not hear this click (will sound like it's coming from the back of the car), then you have a problem somewhere between the controller and the TEMS computer, which would include wiring.
If your TEMS controller seems to be working correctly, follow the directions on the Cygnus website for troubleshooting active driving with TEMS. If there is a problem with the sensors then it will not switch modes when accelerating/decelerating or in tight turns (freeway ramps are good for testing TEMS this way). You can then proceed to the ohmmeter to source out the cause of the trouble.