O2 sensor and catalytic converter replaced now engine cuts off, what is the problem?

Question

Initial code was: PO420 Bad O2 sensor on bank 1 or bad catalytic converter.
After replacing the O2 sensor, engine started cutting off. Would try 2-3 times before it would crank.
Replaced catalytic converter. Still engine cuts off. May start back up immediately or may only start after sitting for a while. May run fine, go out try to crank after sitting for 1 1/2 days and will not crank. Had towed to dealership and car has cranked fine for them. Mechanic has driven and car did not cut off.
Any suggestions?
Have replaced in the following order:
O2 sensor then car started cutting off. did not cut off prior to replacing O2 sensor.
catalytic converter. Car still cut off
Replaced Computer, got bad computer that showed knock sensor needed replacing.
Knock sensor replaced-Mechanic realized it was not bad, but the computer was bad.
Got computer replaced.
Could not load security module.
Took to dealership and got everything loaded.
Car still cuts off.
Took to another shop. Could not find out what was wrong. Car cut off, but not act up long enough for them to find the problem.
Crank sensor replaced per my request.
Got car home. No problem.
Turned car around 2-3 hrs after I got it home - no problem.
Went out 1 1/2 days later and car would not crank.
Had towed to dealership (3rd shop)
Dealership cannot get car to cut off or act up in any manner.
What can the problem be?

Answer 1

What you describe is the VTD (vehicle theft deterent) , this would cause a no crank condition one minute, then later start with no problem . and even crank with no start, to get the code condition you would retrieve the "B" code "B" codes are body control codes. Any engine powertrain code condition will get recorded in its history. What the VTD does is to keep theft from taking the vehcicle , but it is keeping you out of the vehicle. The best fix is to disable the system.