I just bought a 97 GXE (76k miles) yesterday and I was driving home and after a little over 100 miles of driving the Service Engine Soon light came on. I did a diagnostic today and it says its 05 03 (Front Right Heated O2 sensor). I have read in other posts that people have reset the ECU and waited for the light to come back on to double check if it's actually bad, which I'm gonna do and hope for the best. Is there any way of fixing the sensor, like cleaning it off perhaps, or is it an electrical problem and it needs to be replaced? Also does anyone have instructions on how to replace the sensor if need be? Thanks.

Kyle

 

More than likely, if any one of the front two O2 sensors triggers the ECU, it's bad. It's the rear O2 sensor where you can reset the ECU and it will not appear again, unless it continues to trigger the ECU. Usually bad grades of gas can trigger the O2 sensors. Try resetting the ECU, and see if it reappears. If it does, replace it. It's not hard to replace at all. All you need is an O2 sensor socket and a socket wrench and your good to go!

 

I accidently filled up my tank with 87 octane. I had forget to check the fuel door before filling up. If I switch back the next time will is the sensor still bad?

 

This may have tripped the CEL. It all depends how often you run your car with this grade of octane. Our Max's do not like anything less than 91 octane (highly unrecommended). In fact, I had learned the hard way last year when I had trouble getting the car to start at times. It would crank, but would'nt turn over unless I pumped the gas before starting. At times I would end up flooding the engine.....NOT GOOD! I had no CEL codes, so after months and months of driving, figuring what's going on, it appeared to be a faulty O2 sensor (right bank). This was mainly caused from running my car with 89 Octane because 91+ was becoming just too expensive! Well, I had learned my lesson and my car will never see less than 91 Octane ever again!