1999 Windstar 3.8 P0136 & P0141 - Help?

[MasterChief]

I have a 1999 Ford Windstar, 3.8 w 115K miles that has the check engine light on. I used my PocketScan Code Reader to record the following: “P0136, P0141, MIL ON, MONITRS, 0 INC, 8 READY, MISFIRE, FUEL, COMP, CATLYST, EVAP, O2 SNSR, O2 HTR, EGR” I understand that the 136 and 141 codes are indicating a failure of the Downstream 02 sensor bank 1 and downstream O2 sensor heater.

I have two questions for those in the know…..[indent]1) Should I be looking at anything other than just replacing those components?2) Is there anything tricky I should know about the removal and replacement process?

As always I really appreciate those that respond.

[tripletdaddy]

Quite frankly, I'm surprised I'm the first to respond, but I hope I can help enough. You may have a bad sensor where the heater part failed causing the whole thing not to work so giving not one but two codes. However, the two codes could also indicate you have a loose, dirty or corroded connector either at the sensor or upstream of it. If that is your problem, be sure to put dielectric grease in the connectors. Many say these sensors don't fail very often on their own. If you do have to remove it, soak it really good with a rust penetrating fluid and let it sit for awhile. It may not come loose easily. There is a special socket for these things that probably can be rented from your parts store, but I've so far been able to get them just fine with a box or open end wrench. In fact, I didn't find them to be hard at all to remove as others have. When you take it out, be sure to inspect it for any signs of unusual conditions. Green means you have an antifreeze leak into a cylinder on that bank. Very black means it's too rich, which I would expect a code too. I think it should be kind of tan too gray like a normally good spark plug.

[MasterChief]

Thanks! The sensor d/n look too difficult to find and replace. I will check the connections as well. I appreciate your response.

[wiswind]

The downstream is AFTER the catalytic converter.....so if you have antifreeze or oil getting there......it would not look good for the converter condition.

Your '99 may be different than my '96.....but one of my downstream sensors was mounted into the rear of the body of the catalytic converter.......the other 3 sensors were in the pipes.
When I was changing out my catalytic converters (due to rattling inside), I broke the mounting ring for that sensor right out of the converter.
Had I not been changing out the converter........I would have had a problem on my hands.
I was using a oxygen sensor socket (bought at AutoZone) and was being very careful to apply ONLY a turning motion.......and the ring came right out with very little pressure applied.
I had soaked the threads with PBlaster and let them soak.

In your case.....as advised.....I would check the wiring harness.
If you are tight on cash.......you might switch the downstream sensors from side to side.......clear your code(s) and see if the problem moves to the other bank with the sensor.
If you do this.....be very careful to make SURE that the wires get connected back up correctly......very easy to cross wires.....and can be tough to troubleshoot that mistake.

Also make sure that the wires do not hang down and touch the exhaust.

Maybe you will get lucky and only have a dirty connector.

The Oxygen Sensor Socket is not expensive......it is simply a deep socket with a slot on the side.......which permits you to put the socket on the sensor......and have the wires come out the slot.
If you have the room.....a open wrench will work.....just be careful to apply only a turning pressure.......

The downstream sensors ONLY monitor the catalytic converter to make sure that it is working.........they are NOT used to adjust the air/fuel mixture, etc.
Due to their location.....they switch at a much slower speed than the upstream sensors......so they have an easier job.

When working with oxygen sensors.....apply any penetrating oils, etc, ONLY to the threads......do NOT get it onto the body of the sensor.
The oxygen sensor is open to the outside environment.......they work by compairing the air outside to the air inside the exhaust.
So.....if you get stuff into the sensor from outside.....you will seal it off from the outside air......and likely ruin the sensor material in the process.