Toyota Avalon Check Engine insanity

I have a 2000 Toyota Avalon with 160,000 miles. This is my fourth Toyota and I have never had any significant mechanical problems with any before 200,000 miles, until now. The Avalon was purchased new, well maintained and has been running on Mobile One since the first oil change. (I do not suspect bad fuel as all of my cars use the same service station and this is the only one experiencing issues)

Last October, the Check Engine light came on. I was concerned and after a quick cell phone call to confirm it was safe to drive, took it into the dealer. The ?computer? told the dealer of a PO420, the catalytic convert had failed. I was highly skeptical but assured by my service advisor that the computer, chips, software and sensors could not be the problem. But, two weeks after the repair the check engine light goes off again. I am really ticked and take it out on my service advisor who informs me that this is just a coincidence and that the computer tells him about a new error code PO442. He changes the gas cap (gasket) and sends me on my way. Two weeks later the idiot lights go off again. This time the error code is PO440. I don?t authorize fixing this issue and funny thing, after awhile the check engine lights went out. A few weeks later, they came back on. This repeated itself for months until I got fed up with this and took in back in and got a new error message PO171, mass airflow sensor. This was repaired. Guess what, two weeks later the ?lights go off again.

I have already put over $2000 into repairs and have no confidence in my dealers ability to identify and repair my problem. My service advisor finally gave me some good advice, sell the car. Do you have any other suggestions?

Well let me make three suggestions:

  1. The CEL codes only tell you why the light came on. They do not say it is the gas cap or that it is the converter. They only report the results from certain sensors. It is still up to the mechanic to interpret what they really mean.

  2. You should never ignore that light as it may be warning you about something that if not addressed quickly could do serious damage.

  3. Dealers are no better (or worse) than independent mechanics for almost anything you might need done on your car.  They will almost always charge more per hour and often more for parts and supplies.  They also tend to look at repairs a little different than the independent. 

    A dealer may well recommend work that strictly may not be needed, but could be connected to the problem or maybe replace a part when a little repair would fix it ALMOST as good a new.

    There is no need to bring your car to the dealer for any service other than service that is going to be paid for by a recall or original warrantee.

    I suggest that most people would be better off finding a good independent (Not working for a chain) mechanic.

PS all those things may have needed repair. CEL’s will usually go out after so many drive cycles if they do not reoccur, but remember that even if they go out, there was a reason they came on to begin with so everything may not be well.