Oxygen sensor light

[mrsboz]

We brought it to another mechanic. He reset the computer. He checked the whole car over. he said that Windstars are known to do this. My husband drove it for a couple of days and then took it in and it passed right away. Sikked!

 

[BridgetBordeaux]

In the short term this sounds like good news, but you need to be emotionally prepared to deal with the situation again.

We do appreciate the update and all wish that we could just snap our fingers and make the issue go away forever. We have also have had our ups and downs with older vehicles. My car just turned 150,000 miles last week!

 

[P.I. Squirrel]

First, I would like to add to the check engine light on and off subject. The car is controlled by the PCM (computer) which takes inputs from various engine sensors, and adjusts fuel and air accordingly. If the light comes on, that means that at least one of the PCM's inputs are out of whack, and it can't maintain the correct air/fuel ratio. The PCM monitors all the inputs on a constant basis, but will only trigger a code (and the light) if it meets the particular threshold, i.e. after a certain number of trips, over/under a certain voltage. The light will self clear if the parameters return to normal for a certain length of time. This is why your light has cleared. You likely still have a 'history' code in the computer, which can be checked with an OBD-2 scan tool. Unplugging your battery, as suggested by others, will clear the code, but it most definitely will not fix the problem.

Now, for your other problem. If your Windstar has the V6 engine, you will have 4 O2 sensors, one on each exhaust header, and one on each tailpipe aft of the catalytic converter. Those last 2 are monitors of the catalyst ONLY. In other words, if your upstream O2 sensors sense a failure, but your downstream do not, DO NOT waste the money on a new catalytic converter.

Next, the O2 sensors are monitors only. They are usually a symptom of something wrong, but not the cause. Don't waste the money replacing these without first diagnosing the problem. This is where the scan tool comes in. The code will tell you the condition, but not it's cause. For instance, a lean condition (as sensed by the O2 sensor) is very rarely caused by the sensor, but by a vacuum leak, bad intake manifold or head gasket, or EGR valve. There are also other causes, but my point is the O2 sensor is not the problem.

Since the PCM takes a certain number of cycles to validate various sensors, you can not 'fool' an emissions test by clearing the code and driving in for the test. The tester will actually see the PCM validation as 'in progress', and immediately halt the test.

Now, as others have said, kick this mechanic 'friend' to the curb. When you see a doctor for a cold, he can't say 'get a new body', and neither should this mechanic. Take the car to an Autozone or similar auto parts store, and they will plug a scan tool in for free to give you the code.

But remember, just because it has a code, that is the symptom of something failed, but not always the failed part.