P0138 Hyundai -

Question

Hi, I was told by an ASE technician that the po138 does not have to do with faulty rear oxygen sensor. That it is most likely a problem in the Mass Airflow Sensor. So, tell me truthfully, isn't it the mass airflow sensor? I really do appreciate you help!

Answer 1

Hi there,

This code is generated when the rear O2 sensor voltage remains to high. The voltage is produced by the amount of O2 from the converter. If the voltage stays to high, then it's either a short to power or the sensor is no good. The mass air flow sensor should not affect this.