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Hey Everyone,

Just bought a used 2000 with 147k on it. Yep lots of miles but got a really good deal and super clean inside. Anyway, after test drive all good until 40 minutes after buying. P0420 Code came up. Bad CAT or O2 sensor??? Any thoughts? I would not be concerned with it, but I am only getting 19 miles to the gallon with about 85% of miles cruising 75 mph with cruise on (rpms are right for speed). From what I have read in some threads that is low. Granted it has 147,000 miles on it, but that seems low. The car runs and drives great, but I am wondering if the code has something to do with the mpgs or is it just old age? Plugs are new and tires are at 38 to 40 psi.

I want to thank all of you guys. I read many posts before and after buying and they really helped. I look forward to conversing back and forth.
 

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Quite possible you have a bad O2 sensor, that will definitely affect your mileage. Might need to do some more digging to diagnose the problem.

Check the door sticker for your recommended tire pressure, my '02 is 36psi all the way around. Running more air pressure results in a very small increase in fuel economy and a rougher ride, not really worth running crazy air pressure IMHO. My van when I bought it had like 45psi all the way around and drove like it had Flintstone tires on it :).

Dale
 

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19 isn't necessarily bad. It depends a lot on your driving habits and terrain. It is a heavy van and one punch on the accelerator can easily knock a mpg off the tank. How you fill the tank and whether the van is level when filling makes a big difference. Monitor thr mpg over a longer petiod of time to get a better reading on the average. O2 sensers will usually throw their own codes. Analyzing with a good OBDII tester will show their status.
 

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welcome!

Do some searches on here for that P0420 code and start reading!

I would suggest the spark plug non-fouler modification for the secondary O2 sensor which is the one behind the catalytic converter. It has turned off that code for my car for almost three months now (search for "non-fouler").

Your EGR valve and passageways may also need to be cleaned out, which requires removing the upper portion of the intake manifold which isn't that hard of a job.
 
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