'02 with P0171 code getting better mileage?

[atikovi]

Soon after refueling, the check engine light came on and after getting home I scanned it and found the P0171 code for lean operation. The car runs like before but oddly the gas mileage is way up. Ususally I get in the upper 40's but for the last 100 miles it has been over 56 mpg. I'm not complaining but what can I check for this code. After erasing it, it comes back after 10-15 miles. Coincidance that it happened after refueling? Bad fuel? Gas cap problem?

[Patrick Wong]

Originally Posted by atikovi

Soon after refueling, the check engine light came on and after getting home I scanned it and found the P0171 code for lean operation. The car runs like before but oddly the gas mileage is way up. Ususally I get in the upper 40's but for the last 100 miles it has been over 56 mpg. I'm not complaining but what can I check for this code. After erasing it, it comes back after 10-15 miles. Coincidance that it happened after refueling? Bad fuel? Gas cap problem?

You might have one or more of the following problems:


Air induction system

Injector blockage

Mass air flow meter

Engine coolant temperature sensor

Fuel pressure

Gas leakage in exhaust system

Open or short in A/F sensor (bank 1, sensor 1) circuit

A/F sensor (bank 1, sensor 1)

A/F sensor heater (bank 1, sensor 1)

PCV valve and hose

PCV hose connection

ECM

When the engine is running so lean that you actually see an mpg improvement, this may mean that smog emissions are up, with more NOx being formed. Also engine longevity may be impacted when operating under higher combustion chamber temperatures.

Regarding the air induction system, check for a loose oil dipstick or oil filler cap. If not loose, inspect the rubber seals on those two parts.

[NaptownPrius]

Check if your gas cap is on tight. Since it happened after you refueled...I always undo the last thing I did, unless I liked the new MPG.. which I do.