P0161 Downstream Oxygen sensor bank 2 HEATER circuit malfuntion

[ecricky]

Hi
I did the 171\174 repair with the excellent instructions I found on this site and the one with pictures,I found it quite simple and I got the kit for 84.99 on ebay with the valve cover.Now I'm getting the po161 code about the oxygen sensors .I was wondering if anybody has had this code and what they found out,I checked the wiring and it looks good but I need to get further underneath and check better.There's snow on the ground so I'm waiting for decent weather. I have a 2000 sel with the 3.8 in it.
I did a search on here and couldn't find a lot about it but I am not the brightest on the block with forums so excuse me if this has already been covered. thanks

[wiswind]

You did not find much on this because it is not a common problem.
Bank 2 is the FRONT bank of cylinders on your motor.

Easy way to remember is that Bank 1 is the bank with cylinder #1.....which is in the rear bank on the windstar.

Downstream is AFTER the catalytic converter.

The problem could be wiring......dirty connection.....PCM (less likely) or the oxygen sensor.
With the downstream sensors.....it is not so critical to match them....so you would be fine changing just that sensor.
The downstream sensors switch much slower, and the only thing they are used for is to monitor the catalytic converter to make sure that it is working.

If it were an upstream sensor.......as those switch MUCH faster.....and are used for air/fuel mixture adjustment, and add in the fact that oxygen sensors' switching speed slows down slightly as they age........I personally like to change BOTH upstream sensors if 1 needs to be changed so that you end up with both sensors with identical switching charactoristics.

In your case....I would really carefully examine the wiring to see if you might have a loose connection, or wires against the hot exhaust system.
If you don't find anything, you could switch downstream sensors from side to side.....clear the codes (remove negative battery terminal and turn headlights ON and wait about 5 min)....and see if the code comes back......check the code and see if the problem moved with the sensor or stayed the same.
This will tell you if the problem is the sensor or the wiring, etc.

If you have one of those downstream sensors mounted into the back of the catalytic converter body (like one was on my '96) be super careful as when I was changing the "Y" pipe on my vehicle.....the whole threaded part came right out of my catalytic converter body with very little turning only pressure.
That would be a problem....as the metal there is very thin.....and a "Y" pipe is pricey.

A new downstream sensor is not real expensive.....$40-60.

[ecricky]

I had a mechanic check it before I did the 171/174 repair and he replaced 2 of the sensors before I found the part about doing that repair so I've got two new ones on it now. I guess I should ask him which ones he replaced and check those.I will definetly get under there and take a better look and check the wiring,thanks much for the info.

[wiswind]

My guess would be that he replaced the upstream ones....as those are the ones that would have to do with the lean codes (although, as you have found it is almost never the sensors causing the lean codes).

HOWEVER, one thing that can very easily happen, and can drive you crazy is if the sensors were plugged in to the wrong connectors.
It would not make sense to switch the wires between the upstream and downstream sensors though....so that is less likely to be your problem.

One thing that is possible is that the wires got bumped from their correct location (the clips that hold them in place can become brittle with age and heat).
So the under-vehicle inspection that you mentioned would be an excellent next step.

[ecricky]

okay,so tonight I put it in the garage and put the jack stand under it and started looking around,I didn't find anything wrong with the wiring for the bank 2 sensor and it actually looks newer then the other one,I think I could almost plug the bank 1 into 2 and vice versa but I didn't know if that would hurt them or not. I guess the next step is to switch them around and see if it stays the same or moves with it.
Whats the best stuff to spray in there and loosen them up? I want to be careful not to strip out the y pipe considering how expensive they are. Thanks