Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

Engine Check Light

Awhile back my check light came on and I had it checked out. The scanner said it was a O2 sensor. I had it replaced but the light came back on. The mechanic said I need the computer re-flashed and if that does not work then I need a new computer. Are they telling me the truth? or are they giving me the run around?

Run very far and fast from that - ahem - “mechanic.”

There are no codes that tell you to replace an O2 sensor - unless by “scanner” you mean that the O2 sensors were actually scoped.

As long as you’re not in CA, go to any large auto parts chain store (e.g. Autozone). Have them scan it for codes (free). Write down the exact code number - e.g. P1234

Post it here along with full car info - year, mileage, basic maintenance history info, any weird things it does etc.

I did take it to Autozone today and the code came back P050 which is the O2 Sensor they replaced (Bank 2 Sensor 1). The car is a 2005 Hyundai Sonata GLS V6. It does not do anything wierd only problem is the check engine light is on. I also notice my fuel mileage is not what is use to be.

The code doesn’t say that a sensor is bad. It says that a sensor is reading something outside the expected value. This can be due to the sensor failing (which is what everyone blindly assumes) or it can be due to the sensor being accurate and indicating that whatever it monitors is having a problem. There’s a diagnostic procedure that should be followed by the mechanic to figure out what’s really wrong.

a 2005 Hyundai should be covered, no?

I have to assume that is P0050 rather than P050.

This might indicate that the problem is in the sensor (like anything else, new onese can be bad off the shelf though that is not so likely) or it might be in the wiring for the sensor. Someone needs to check the whole circuit that feeds the sensor.

I don’t know if it applies, but for Hondas, you normally have to buy the original OEM replacements sensor because other after markets still make the check engine come on. My experience on my Honda. I wonder if that is the case with Huyndais.

The computer does not like what the oxygen sensor is telling it…It could be a bad sensor, a bad connection, faulty/damaged wiring, or the computer itself…

A “universal replacement” (U wire up the connector) sensor might not make the factory computer happy. It will take a real pro to sort it out…