QuestionMy wife purchased a 1997 Tiberon FX, it had a check engine light with a code of P1128, the dealer here in Mechanicsburg changed the Fuel Metering Senor when the previous owner had it looked at by them. When I had the code read at Auto Zone, they checked their computer for codes, and it showed a "Heated O2 sensors swapped". What does this mean and if it is a bad sensor, which one should I start with, the one before or the one after the CC?
AnswerHyundai has no code which means "heated O2 sensors swapped." Assuming the P1128 is still present, it means that the Engine Control Module (ECM) must deliver more fuel to maintain proper mixture than it thinks should be required when under load. Most frequently, this is caused by a faulty air flow sensor or a leak allowing unmeasured air to enter the engine. I'm presuming that by "fuel metering sensor," you mean oxygen sensor. While that's a possible cause of the P1128 code, the frequency of that occurrence is near zero.
First, check for vacuum leaks, especially in the PCV hose.
Second, check the air bellows between the air flow sensor and the throttle body. Make sure that it has no breaks or leaks and is securely attached to the throttle body and air flow sensor.
If the above is okay, you probably need a new air flow sensor.
