Ford 2002 Windstar engine light on

[DavidChen]

All,

Recently, my Ford 2002 Windstar engine light is on. I went to Auto parts store, they used computer checked. I forgot the code. However, it indicated the problem is the oxygen sensor.

Windstar has two oxygen sensors. My question is do I need change both
oxygen sensors? Each oxgen sensor is cost about $50.

Any comment?

Thanks.

David

[DRW1000]

Go get the codes read again and write down the actual error. Often an O2 sensor gives a non-normal value and is blamed as the cause but normally the O2 is reading correctly and there is a problem upstream that is causing the actual conditions reported by the O2 sensors.

We don'r have autozones up here in Canada but I have read numerous instances where the autozone folks read the codes and suggest an O2 sensor when in reality it is not an O2 sensor failure.

[way2old]

Are the codes P0171, P0174? If so you have a vacuum leak somewhere. Do as DRW1000 suggested and post the code numbers back here. Parts stores are in the business of SELLING parts, not diagnosing.

[DavidChen]

The error code is P0174 - System too lean (bank #2) and auto parts recommends me change two oxygen sensors.

Any suggestion?

[DRW1000]

Yes,

Do a search under P171/174 or Isolator bolts in this forums. There are volumes of posts on this topic. Often it is not an O2 sensor failure. There is a TSB (technical service bulletin) for this failure in 99-03 models.

What most of us disover is that we have a leak in the intake system that is letting air into the intake stream that has obviously bypassed the MAF. This means that the PCM (computer) thinks there should be a specific amount of airflow and allows the correct amount of fuel into each port yet the O2 sensors read this as lean.

You only have 174 so perhaps you do have a different problem (even a bad O2 sensor) but my guess is that the leak is small and one sensor is a bit more sensitive or more "extra" air is getting to that bank. If I were a betting man I would bet that you will get code 171 soon too.

It is a bit of an involved job to repair but certainly not out of the range of many. Have a look at other posts and post back any questions. We are always willing to help and many of us have had this exact problem.

[busboy4]

Hi David
If you get into oxygen sensor changes, note that on the '96 3.8L engine there are four oxygen sensors and I assume it is the same with your later model. One upstream and one downstream for each bank of cylinders. Each of the O2 sensors can trip a specific code to identify which one is failing. I would not go blindly changing O2 sensors without a specific code.

Good luck

[DRW1000]

The other thing you could do if you were really adventurous is two swap the left bank sensor(s) with the rights and see if the code follows the sensor or stays with the bank.

[watchful123]

I had a P171 code on my '96. It ended up being a vacuum leak in the PVC hose from the intake. As DRW1000 says, a vacuum leak will cause the O2 sensor to read out of range, even if they are good. I would check thoroughly for vacuum leaks before spending any cash.