Technician A says if a lean condition caused by a vacuum leak, restricted injectors, dirty MAF, clogged fuel filter, or bad fuel pump exists, the LTFT will have a negative number. Technician B says when the O2 sensor has a rich signal, the STFT goes lean to adjust the air/fuel ratio. Who is correct?

Question

Quizplus · Accepted Answer

A lean condition would cause the LTFT to have a positive number as the system adds fuel to compensate. Technician B is correct because when the O2 sensor detects a rich condition, the STFT will decrease fuel to adjust the air/fuel ratio.

Technician a Says If a Lean Condition Caused by a Vacuum