I found that my car's transmission is shifting hard and the "Traction Off" light stays on. It only shifts hard when the light is on (once in a blue moon it goes off). I thought I cleaned the MAF sensor well, but apparently not. Would an O2 Sensor be the cause of the hard shifts? I had it checked and I had O2 Sensor, Catalytic Converter, and MAF Sensor codes. I'm a college student so I can't really afford to replace all of these things at once. Please help!!