I want to begin by saying I am the proud new owner of a 2005 MC. I just bought it last week and love it so far. However, the SES light has already came on! First it was for the pre-cat O2 sensor and a small EVAP leak, which I was told could just be the gas cap. So, I replaced the upstream sensor and the light went out. Now today the SES light came back on so I took it to Autozone again for diagnostics and three codes showed up. One was for the pre-cat O2 sensor (which is now brand new), the other was for the post-cat O2 sensor, and the final one was for a small leak in the EVAP system. Has anyone else experienced these three codes simultaneously? What might be some problems/ideas to go about getting this taken care of? I am pretty handy mechanically and generally take the DIY route with repairs.

 

if its an 05 I would take it too a dealer as your o2 sensors are probably covered under the warranty extension if it does indeed need new sensors.

 

Yes, they are still covered under the warranty. I was thinking that there might be another problem, though. It is extremely rare to have both O2 sensors go bad simultaneously and I had just replaced the upstream sensor. There's no way it could have gone bad in one day's time. I'm thinking my engine might be running lean?

 

You need to find out what your adaptations are at. This will tell ya if your lean or rich. Then once you correct the issue you will need to clear the adaptations or the SES will just reset after 2 drive cycles. Its impossible to even guess whats going on without more info.

 

Agreed, It could be related to fuel pressure or a faulty MAP sensor.
Your 02 sensors are probably fine.

 

Sorry if this is a stupid question, but what do you mean by adaptations and how would I go about checking them?