torque converter

I have just had my trans rebuilt by aamco and at $2400 I was dissapointed to find out it was not going to have a warranty as my lockup torque converter was not working. I have searched the web over and over and found a bunch of tests to do from www.autorepair.about.com/cs/troubleshooting/a/aa061701a_p.htm
I have got to the test on checking the solenoid and have no clue where it is?
Also can someone tell me if the computer ECM unit controls the TCC solenoid if so do the compters go bad?
Any help greatly appreciated

What year is the truck? The computer controls lockup in all the years these trucks were made. First need to know the year of the truck. For '95 and up, if the TCC is not locking up and the computer has not other codes that will cause a non-lockup condition, then the computer will set the P1870-component slipping code. You have to scan the computer first to see if something is stored there, or any pending codes. '94 and lower are different set of codes and scenarios. The computer could go bad, but that is unlikely, but it could happen.