Expert: Sean Halliday - 4/23/2009

Question
Check Engine light came on car, it turns off almost everytime I stop.  I have to restart the car.  My dad checked and this code came up P0171 generic system to lean Bank 1. Can you please tell me what this code means.  Also where is the Bank 1 in the engine.


Answer
This could be a oxygen sensor problem on the intake on bank 1.The sensor controls the intake of fuel mixture on the engine.On your car there are 4,2 before the converter and 2 after.The one you will need to change will be before the catalytic converter.Other causes can be a leak at the intake or vacuum leak.This will need to be diagnosed properly as the sensors are not cheap and if you run the car on a lean mix,you can cause serious engine damage.Bank 1 is usually left side,bank 2 is the right as you sit in the car(V8).If you have a transverse(V6) engine bank 1 will be front and bank 2 the rear.