Mechanics

CHECK ENGINE LIGHT IS ON

2005 Toyota Corolla

Engine Performance problem
2005 Toyota Corolla 4 cyl Front Wheel Drive Automatic 77000 miles

scan code is P0171 - system too lean. What does that mean? Do I need to replace the O2 sensor, or is it something else?
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Mrronald
January 14, 2010.



The upstream O2 sensor is reading a lean fuel mixture, this could be an O2 sensor, clogged injector, low fuel pressure.

I would replace the O2 sensor, erase code. If code reappears, then measure fuel pressure with mechanical gauge to start.

I would also add a can of SeaFoam after changing O2 sensor to gas tank.

Mmprince4000
Jan 15, 2010.