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Jim Grant's Tech Tips
00 Hyundai, Needed Sensor?
Q:
Did I get taken? My “Check Engine Light” came on my ‘00 Hyundai. The garage said, according to the computer readout, that I needed a new oxygen sensor. The garage replaced it, cleared the computer code and yup, 3 days later the “Check Engine Light” came on again. The garage then told me it was because of a leak in my exhaust pipe. They fixed the exhaust. The “Check Engine Light” has not come back on since (it’s been a week). My question is-did I really need a new oxygen sensor??? Or was it the leaky exhaust pipe to begin with? Sincerely, a middle-aged female driver..
A:
Did you really? Can’t say without a bit more information. First, your vehicle, if it has a 4-cylinder engine, has 2 Oxygen sensors. This leads to the question, what was the first computer code? The next question is what was the second computer code? The check engine light can come on for over 200 different codes. Oxygen sensor codes are just a small piece of those many possible computer codes. If the second code was the same as the first then there is the possibility that the oxygen sensor was not the problem. And yes, an air leak in the exhaust can cause the computer to set false oxygen sensor codes. You should never count on a computer’s diagnostic code, those silicone-based life forms are not worthy nor can they be trusted with the information they provide. We recently had a perfect example in the shop. The computer in this 4 cylinder Nissan (which has 4 oxygen sensors) had a code indicating that one of the oxygen sensors was not working correctly. The check engine light was on and the code identified a single sensor as being the problem child. Due to our lack of computer trust the sensor was not replaced, but it was tested, this takes time. Oxygen sensors have a defined range and reaction time. Performing these tests on the accused sensor found that the sensor was working correctly. What now? The computer says bad, but the sensor tests good? To bring the story to a quick end it was found that another sensor, not any of the oxygen sensors, was reading incorrectly. There was over 2 hours of diagnostic time needed to prove that the code was pointing to the wrong component. I’ve found that many people believe that the computer tells the mechanic what is broken. Sometimes it’s that simple, but it doesn’t happen that often. Yes, the leaking exhaust could set a false oxygen sensor code. If the code that returned was the same as the first, I doubt you were intentionally taken. Why do you think I don’t trust computers?
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