A few months ago, I noticed an issue my 2008 sx4 base sedan 5 speed MT 2.0L. I was having cranking issues and eventually my battery died. I jumped it and drove the car that day. I had problems with the car shutting off at low idle speeds. Even as bad as shutting off when I put the car in neutral to coast to a stop sign/light or make a turn. It stopped doing that after about a day so I thought it was related to the battery issue. I bought a new battery and that fixed the cranking issue. When I installed the new battery, I went through the the same ordeal with the car shutting off at low idle or when put into neutral. Once again, it righted itself after about a day of driving. I figured the battery being disconnected caused something to reset and once the car was running again, it had to relearn something to get it running correctly again. Didn't have the problem until recently. I was reading up on my cel light code. P0420. Tried a few easy steps like filling up with 89 octane gas, cleaning the maf sensor, and cleaning corrosion off of the battery terminals. Well when I disconnected the battery to clean the terminals, I reset whatever it is that resets and I had to deal with the car shutting off again today. My cel eventually came back on today on my way home from work. Car still hasn't righted itself yet. But I expect it to do that tomorrow. I'm wondering if this issue with the car shutting off in neutral is related to the p0420 code I get. I assume my cat needs to be replaced, or some have even said the 02 sensor but both are pretty expensive and don't expect to be able to afford that anytime soon. Could the two be related and point me in a direction that would be a cheaper fix than replacing the cat or 02 sensor, or could a bad 02 sensor cause the shutting off issue? Any experience with this?