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Do I need an O2 sensor?


I have a 1997 Dodge Intrepid which seems to be running fine. Yesterday the Check Engine light came on, so today I took it to a mechanic. He brought out a little hand-held device that reads the computer codes, and it said that it was the O2 sensor. He said that to get a new O2 sensor would be a waste of $400, turned off the Check Engine light, and sent me on my way. Was he right? Is there any danger in not getting the O2 sensor replaced? Thank you.

That check engine light indicates that the engine computer has a DIAGNOSTIC CODE stored. Diagnostic, in this case, means there is a problem in a certain circuit. The scan tool pulls that diagnostic code from the engine computer. It’s up to the knowledgeable mechanic to do the diagnosis to determine the cause. A simple code scanner is inadequate for the task (of looking at the oxygen sensor performance).
The oxygen sensor may be faulty, but, to just say it is, from the trouble code, is just a crap-shoot.
Here are some oxygen sensors:,16100117/shopping/partTypeResultSet.htm What prices do you see?

Also, you only need to fix this if your gas mileage and/or converter lifespan are important to you.

I haven’t heard of O2 sensors costing $400.

If (when) the light comes back on take the vehicle to another mechanic and see what he or she says. If the light does not come back on, don’t worry about it.

Before changing any parts make sure there’s no exhaust leak. Hold a rag over the tail pipe. There should be a pressure build up and no hissing.

In some states like NH any stored codes will FAIL the emissions inspection. If the light keeps coming on you’ll need to get it fixed.

Well, depending on you engine and exhaust configuration you may have 4 or 5 O2 sensors, please see if you can tell us the code, your engine (3.5 or 3.3) and if you have dual exhaust pipes, so we can pinpoint the location. Thank you.

The mechanic cleared the code out. If it reappears have it checked by him once again and at that time if ever you should actually fix the problem if you don’t notice any running problems.

If its a significant issue the light will come back on.

I haven’t heard of O2 sensors costing $400.

I have heard of OEM Oxygen sensors costing that much, especially for a Honda or a Toyota.

timtrowbridge, I think you can buy a universal Oxygen sensor at Auto Zone for less than $100. Also, I would check out the prices for an Oxygen sensor for your vehicle. Your mechanic might be wrong about the cost.

timtrowbridge, that “check engine” light is more important than you think. A solid light indicates a minor problem like a bad Oxygen Sensor. A flashing “check engine” light indicates a serious problem that you should not ignore. So it would be in your interest to put up with that solid “check engine” light shining in your face rather than disable the light. Leaving it disabled could cost you.

Oxygen sensors are easy to replace, especially if you buy the special socket or wrench. You could probably do this yourself.