P0431 and P0421 codes?

Strange that is has bank 2 on a 4 cylinder since there is only bank 1, hmm anyway I would check the engine cooling system thermostat, does the car have a engine temperature gauge, and if so does it stay on the cold side for a long time? This can mean the engine is not warming up fast enough and it will give you these codes.

P0421 - Warm-Up Catalyst Efficiency Below Threshold (Bank 1)
P0431 - Warm-Up Catalyst Efficiency Below Threshold (Bank 2)

If you find the thermostat stuck open replace it and then clear the codes which should fix the problem. Please upload a short video in your response of the problem, so I can see what's going on :)

1 hour of driving. Back roads and minimal highway.

After riding for an hour in morning 29 degrees

hmm sorry this website is having an issue so I cant see the images can you just tell me where the needle is, or you can upload a short video those are working.

Picture of scanner readings. Before and after pics of fuel gauge.

Temp took from 4:21pm to 4:43 to reach mid point of temp gauge on dash

Yep, way to long, it should be at operating temperature with in 5-7 minutes, I would install a new thermostat and then clear the codes. Can you just tell, (type) me the codes?

P0431 and p0421

lol sorry, I thought here were more codes then what was listed, after doing more research I found that the Galant 2.4 is notorious for the front cat (manifold cat) going bad. When both P0421 and P0431 show together, that’s classic. So you replaced the front or rear cat?

Replaced front cat. I thought it only has 1? I replaced all 4 02sensors and cat

All 1 piece

Sorry, the site is still having an issue, so the front cat is made into the exhaust manifold, is that what you replaced? If not this will be the problem.

Yes sir

So is this a v6 engine?

2.4 inline 4

Picture of catalytic converter

It is so strange that you have bank 2 on a four cylinder, some generic scan tools will label downstream sensors as "Bank 2" or assign “Bank 2” codes to rear/secondary oxygen sensors. If so if you had these codes before the cat swap and you still have them I would say the PCM is bad. I would remove it and send it out for testing.

Ok thanks

Please let me know what happens.

Yessir