double code 404 and 420
 

ok i got this 05 pacifica 3.5L auto awd car and it had the cel on with 2 codes. p0420 and p0404
p0404 looks like a egr valve issue and p0420 has something to do with the cat. it also had a p0457 that was for the gas cap but i put on a different cap and the gas cap loose message is still on but they say it takes 3 drive cycles to self clear. i did not see it in the codes when i checked them after changing the cap and driving it 15 miles or so. but this is my question will the p0404 egr issues cause the cat to throw a code? the car has 105000 miles but i have had cars with way more miles and no cat issues. so what do you guys think the egr causing the cat issue? thanks

My 05 cat lasted about 98k miles but only thru a 420 code. With the amount of oil these engines burn I was surprised it lasted that long.