My wife has a 2000 Corolla, which currently has a little over 77,200 miles on it. Back in September of last year (about 4 months ago), the Check Engine Light came on. We took it in and had it checked, and the mechanic replaced the oxygen sensor and the mass air flow sensor. The light stayed off for a few days, then came back on.

We took it in again and were told they tighten the MAF sensor. Again the light was off for a few days, then came back on. This time we were told that the spark plugs needed to be replaced, and we did that. Again, the light was off for a few days or so, then came back on. It would go off now and then, but was mainly on.

So, we took it back in one more time today (same mechanic, different manager), and we were told that the catalytic converter and the *other* oxygen sensor needs to be replaced.

The total cost we were given for this is $721 plus tax. They broke it down as $186 for the "After Catalytic Converter Oxygen Sensor" and $535 for the Catalytic Converter. Is this a reasonable price for these services? Also, any thoughts on the diagnosis, and/or whether any of this might be covered under the Certified Warranty?

Thank you!

- Randy

Take it somewhere else. Your machanic has no troubleshooting skills and is just swaping parts at your expense.

A good mechanic should be able to tell you the code, have a plan how to troubleshoot, and demonstrate what part is defective and why. If doen't seem to be the case from your description. But it is hard to find good mechanics these days.

If you don't know the specific problem code, nobody will be able to provide you a valid advice.

Yes, MAF and O2 sensors fail relatively frequently (or are just dirty) in average car with MAF. Cats fail rarely at this milage unless you used leaded fuel or the car was totally out of tune or burning tons of oil or other contaminants.

It would be helpful to us and we could help you better if you could tell us the fault code. You could try to take it to Autozone and they have a diagnostic tool that reads the fault codes and can also resets them. This site - http://www.troublecodes.net/Toyota/ld - may help you with the faulty component. Sensors are easy to change (at least when you know which one they are and where they are located on your car). The catalytic converter is also easy to change, although they can be expensive. The dealer of course has to charge you the labor cost as well as the cost of the parts and that makes for a good sized bill. If your mechanic just changes what he thinks is wrong and it is not correct so the CEL keeps coming back, then it will get expensive. I am not sure what part of it is covered by your warranty. You would have to check the details that are in the warranty information. Hope this helps.

Check the emissions warranty. Some items are covered 8 years/80K.

OK, I have a little bit more information. 1st, the code is "P0171 - System too Lean". Second, as I checked our repair records, we did not ahve the Mass Air Flow sensor replaced, it was the Coolant Temperature Sensor.

Hope that helps with the help.