Ok so where to start.... I have a P0420 code that's popping up and after about 30 minutes of driving my van starts to overheat which is no bueno because that's how far my commute is...
Anyways I started off with the obvious and replaced the thermostat. That didn't work.
The the thermal sensor was replaced. No go.
Water pump was replaced in aug 2015.
New upper radiator hose and distributor cap put on in October 2015.
And just this week after totally giving up and ready to kick the dang thing I took ol' blue to the Mechanic and they replaced the catalytic converter.
I definitely have more power now but after just a couple days my check engine light came on again and the overheating problem started all over again.
So I have 2 theories :
1) downstream O2 sensor (fingers crossed cuz it's cheaper!!)
2) radiator needs replaced

So anyways I need some help! Can the O2 sensor cause the engine to overheat or is that a separate issue altogether?

 

O2 sensor will not cause overheating. Get the radiator checked out. Are the cooling fans coming on?

 

Yes the fans are coming on. It seems like when I'm sitting in traffic or going at lower speeds the overheating is an issue. Maybe a clogged radiator? I didn't figure the O2 sensor would cause overheating aft er researching it more.

 

I would check the radiator.