Limp mode?

The scanner kicked out these two codes: P0420 and P0706. Any help will be much appreciated.

The car has a new catalytic converter on it and still stalls out like I said before. Was thinking it could be the TCM. Your thoughts?

The NSS is fine. Car runs and gears work fine. Problem is when driving it seems to stall but engine is still running. It just has no throttle response. You can shut it off and wait about 15 minutes and it will start and run about 5 mile or so and repeat same stall again. I have reset the ECM and it runs okay a few days then starts same thing again. It's starting to get on my time to get rid of it list.

Replaced it but still have same problem. Guess it is something no one can solve.

This doesn't make any since. Had a new cat put on and had same problem. So I had them replace the new cat as defective and put another one on. Cured the problem. Who knew. Thanks for your help guys.

I bought a 2009 chevy aveo LT 2 years ago and noticed the trans wasn't shifting right and there were other noises. I replaced the O2 sensors and was told the rings in the trans were being worn down when it slips causing my fluid to turn black. I have had the fluid flushed and filter replaced 3 times since. My current problem started this past winter when the hold light would come on and flash causing the trans to not shift into higher gears. Then 2 months ago the check engine light came on also. After that the car started to lose power and shake. We replaced the plugs and coil pack fixing the power and shaking but the hold light and check engine light came back on only this time I don't seem to have the shifting problem but the temp gauge and air condition stop working when the lights are on which is 99% of the time. Any ideas? I know it is called limp home mode caused by faulty sensors but where do I start?

It reads 3 codes but all are the same. P0128 coolant thermostat (coolant temp below thermostat regulating temp). Does the thermostat need replaced or is it reading this because the gauge isn't working?

I bought a code reader and did it myself.

I have an 09 aveo stuck in lomp mode. It happened after a hot pos cable came into direct contact with the trans directly. I replaced every accessible trans sensor with no change, tested to make sure I had ref voltage going to all sensors and finally replaced the tcm. Only to have it not communicate. Gm dealership said that the tcm needs no programming and shout work out of the box. Which is contrary to everything ive heard. I contacted a trans specialist in town who assured me that it did need to be programmed or "flashed" however after he had my car for a few weeks he called and told me that the tcm I bought is not right. And it doesnt contain the propper programming for my car. Its a 2009 chevy aveo ls. 1.6 litre with alsin 4 speed. The shop told me that the car I have was actually produced in south korea and is more of a daewoo than a chevy. So what it boils down to, im almost positive the tcm is the issue ( no speedo stuck in third. No hold light") I just need to know if there really is daewoo progaming for my 2009 chevy and where can I find it?