DTC P0171: System Too Lean (Bank 1): DTC Detecting Condition

Breaking the lambda adaptation and lambda controller limits for a long time, which may have been caused by failures in the fuel or intake system will involve emission rise and therefore shall be diagnosed by fuel system monitoring. The lambda controller deviation including adaptive terms are used for fuel system monitoring. The time counter is increased if lambda controller exceeds the threshold and the ECM sets DTC P0171 or P0172 respectively depending on direction of lambda controller deviation. P0171 is set with positive deviation and P0172 is set with negative deviation. If same error code is set in the next driving cycle, the ECM illuminates the MIL.