2002 Sienna check engine light

Every few months my wife’s Sienna check engine light comes on. The 1st time was just after a stom in Maine June, 2010. She took the Sienna to a local shop and asked them to check it out. They connected it to their computer and could find nothing wrong and were able to turn the alarm off. a few months went by, she had the car inspected in August at the Toyota dealer and a week later the check engine light came on again.(I think after a storm but am not sure) She had the dealer hook the car up to the computer and they told her that it was one or all of the following: catalytic converter, computer, or oxygen sensor. They told her it would cost thousands of dollars to fix and they would not pass the car’s inspection next year because there was no history stored in the computer. They did however, turn off the alarm. We had no issues until last week. My son was driving the car to NH during a snow storm in heavy traffic.(Jan, 2011) He stopped to take a break, got back in the car and the check engine light came back on. The car runs well. Other then the warning light seems fine. The lightseems to come on when there are storms or during low pressure systems. Could that be messing with any of the sensors or the computer? Another ongoing problem is that the low tire pressure light comes on regularly, and the dealer has never been able to fix it. Could the 2 be part of the same problem? I don’t have thousands to spend on Toyota replacing things until one of the replacements fixes the problem. Can anyone offer me some advice?

When the check engine light comes on again, go to a local auto parts store like Auto Zone that will read the code for free. Write down the exact code (a series of letters and numbers), not just what they tell you it means. Without the exact code, it’s difficult for anyone on this site to tell you what’s happening.

But based on what the dealer told you, most likely it’s a code from an oxygen sensor. The sensor may need replacement. I’d take the car to a trusted mechanic who has the diagnostic equipment to test the oxygen sensor(s). He should be able to tell you whether the sensor(s) are OK or if one needs to be replaced.

Thanks. My son has the car. I’ll have him get the codes.

Please add a little punctuation. Using Paragraphs would help. Take a look at a news paper. They always have double spaces between paragraphs and tend towards short paragraphs. It makes navigating your message a lot easier.

Now about the car. If the dealer can’t fix it, you find a mechanic who can.

   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.  During the warranty period be sure to have all required (as listed in the owner's manual) maintenance done and to document all maintenance work.

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

Note: Never ever use a quick oil change place. They are fast cheap and very very bad.

If I have missed an important part of your message, sorry. Let me know. Also note that you may be able to read a error message, even if the light is off. It does not always work, but it is worth a try.