Service Engine Codes: P0741 and P0603
 

I have a 1999 Seville. I got service engine soon on my dashboard last night on a long drive. I took it in today and the auto zone told me it was codes: p0741 and p0603. From what I read I looks like the p0741 is not a big deal and can wait, but I was not sure about p0603 code. From what the guy told me at the store it is for sure the ECM and that it was part of the computer part of the car. My car is running prefect from what I can tell.

How import is it to replace the ECM if the car is running prefect and is it something one can do himself?

Thanks

P0741 is a TCC code kind of a big deal, normally expensive to correct. P0603 is a PCM memory reset error not a big deal won't hurt anything.

I also have the P0741 code that comes on when I drive normally. However If I drive like a hot-rod the light goes off until I resume normal driving. The car performs great and I do not feel or hear anything wrong. I wonder if changing the transmission oil will clear the
problem? - Anyone have any experience with the TCC?