Questions and Answers

O2 Sensors Fix Themselves Q. Vincent, I found your site to be very informative. I do have a question though about my car. I drive a 1996 Toyota Camry 4 cylinder, 2.2 liter engine. It has an automatic transmission, fuel-injected engine (I believe). The mileage is at about 120,000. It has cruise control, no ABS brakes. I'm not sure about rack/pinion steering.

Anyway a few weeks ago, the "check engine" light came on. I got a diagnostic done of the car, and the mechanic said that the Oxygen Sensors (there are two in this car) were malfunctioning. They took them out in anticipation of replacing them, but the supply store sent them the wrong parts, so they put in the old ones and sent me home. Without getting anything further done to the Oxygen Sensors, the "check engine" light--which had been on the entire time--mysteriously turned off. It has not turned back on in a week or so.

Now the "check engine" has not turned on since them. My question is, did something happen to the car that replacing these is no longer necessary? Did perhaps the mechanic mis-diagnose the problem, and now the car is alright? Should I get any further work done to it? As you know, replacing the Oxygen Sensors is an expensive procedure, and if I can get out of having this done without hurting the car, I would like to.

Thank you very much for your help,
Jude

A. I have seen things like this happen without much of an explanation why it happens. The most likely possibility is that there was a bad connection and by removing the O2 sensors and reinstalling them, it improved the connection enough to start working again.

At any rate, as long as they are working I wouldn't worry about it and if the check engine light should come on again, you'll know where to look first.

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