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I have a fault code (p0420)catalyst system efficiency below it has my check engine light

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I have a fault code (p0420)catalyst system efficiency below threshold (bank 1), exactly what am i needing also I've done a complete tune up and still lucky to get only about 320 340 miles to a full tank is this the right MPG
hello, what is the year and model and engine size please, thanks,tim
Customer: replied 8 years ago.
Sorry about that Tim 1998 Dodge Grand Caravan 3.0l 130k

hello, the best thing to do is to replace the upstream and downstream oxygen sensors and reset the computer by doing a negative battery terminal disconnect ,tim


this should increase fuel milage by 2-4 mpgs

Customer: replied 8 years ago.
Now as far as mpg 340 a full tank is that normal and with replacing the Oxygen Sensors would help get better gas?

can you give me the last eight of the vin and i can check the fuel tank size

and yes-- o2 sensors will increase mpg

Customer: replied 8 years ago.
wr708408 vin and with computer reset just take off the negative battery terminal with the van off for a few mins right?

sean, i double checked -- they only list one fuel tank for this year minivans -- 20 gallons-- this= 17 mpg -- this is not very good -- average should be between 22-24 mpg for this year van,tim


replacing the sensors and resetting computer will improve your avg mpg,tim


yes on the computer reset

Customer: replied 8 years ago.

I replaced spark plugs Champion oem labled under the hood with new wires cap and rotor and idea and now with the o2 that I have not done now would that make that much of a difference

the 02 senors control the air fuel mixture-- in not fucntioning properly can lead to excessive fuel consumption
Customer: replied 8 years ago.

So that could be the real big real why I'm only getting 340 a full tank and when I had the tune up done I replaced the air filter and pcv as well and oil changed so great that's what I will do change both o2 sencors and see if that helps......

i am sure you will see an improvement, thanks and take care tim
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