I have a Saturn L300 2003. A few weeks ago my check engine light came on. I went to Auto Zone. They printed out the code to me:

“catalyst efficiency low-bank 2; the oxygen sensors for the catalytic converters”. OEM Number to cross: P0431"

They said its the sensor, now my car has two one in the front and back. I checked with a few mechanics and they all said that the front one is cheapest. The mechanic said if I gave him the code he could tell me which it is. Well I Gave him the code and haven’t heard back in 2 weeks. Can anyone tell me which it is? I found information out on how to change the sensor and its very easy if its the front. Please help! I want to fix my car!

Does your car have a 4 or a 6 ?

its a 6.

Have you tried simply resetting the light? This “fault” might just disappear into thin air…

Do you think its worth 75 bucks to have someone look at it atleast?