Just got a new code today. P0141, I pulled the code with my code reader and it read "O2 sensor heater circuit malfunction (bank 1 sensor 2).

No change to truck performance or engine sounds etc.

I am hoping that someone out there can help me with this one. How do I go about diagnosing this? What does "bank1" and "sensor 2" refer to? What is the heater circuit? If anyone can give me a quick auto shop description of this system that would be great too.

I know that the O2 sensors measure the O2 levels before and after the catalyst and sends back messages to the computer to adjust combustion etc.

I havn't done anything with this yet, except pull the code. It's unusually cold here right now, so I don't really want to crawl under my truck and have a look at the oxygen sensors till it gets a bit warmer and the snow dissappears.

Thanks a lot, this forum has been great for this type of thing.

Ron

 

O2 sensors have "pre-heaters" built into them. Not exactly sure how and why they work, but appearantly <b>yours</b> isn't
Can't help you in the bank1 sensor2, but I know there are 3 or 4 O2 sensors, so someone should be able to tell you which one it is, so you can replace.

 

This might help: Ford 02 Sensor Location

Bank 1 = Passenger Side

Sensor 2 = Rear Sensor (after the cat)

 

Thanks for the reply, Rockledge. I understand where your talking about, passenger side, after the cat. Is that just a generic schematic for all Ford's? I don't know for sure, but I didn't think my 4.0L Ranger had a cat on the drivers side. If I remember correctly, both sides of the exhaust come together near the passenger side, then it's just one pipe, thru 2 cats, then out the tailpipe.

Just want to make sure I replace the right one.


Thanks again,

Ron

 

To be honest Ron, I'm not sure how many HO2S you are going to find on your 1995 Ranger. That is the year that Ford switched from OBD-I to OBD-II engine managment systems so there might even be a few different configurations out there for that year Ranger.

In any case, "Sensor 2" is always the rear sensor, so if you only find 2 HO2S sensors on your truck, then you'll know that it's the rear sensor that set the code.

 

Ok, makes sense to me now. I'll have a look tomorrow and order a new one from the parts store. Any tricks to removing/replacing it? Looks like it just threads in similar to a sparkplug or sending unit. Haynes manual suggests some anit-seize compound on the threads.

Sure glad I purchased that code reader, saved me a bundle already!


Ron

 

I like my code reader, as well.

Your truck is at an age where, if the O2 sensors have never been replaced before, then they are going to be a bit stubborn. I suggest spraying them down the night before with PB Blaster or some other bolt breaker fluid. Then the next day you want to run the truck a little to get the exhaust system warm, but not hot, if that is possible. Then spray ithe sensor(s) some more with fluid, unhook the electrical connectors, and go at it. They even rent special O2 sensor sockets at most parts stores if you are not comfortable using a wrench on the sensors.

Most new 02 sensors already come with some copper based anti-seize on the threads, but you might want to grab a small packet just in case.

Finally, it's not my money of course , but I would recommend that you replace BOTH oxygen sensors, if they are original (assuming you only have two).

Good luck!

 

I have a 95 4.0L as well, just recently changed the O2 sensors. There were three, two before, one after the cat. I bought motorcraft sensors (three), all had antisieze on them. Also got a specialty socket and that was a big help. I was expecting a struggle, but was very easy, didnt have to use PB blaster or anything although I bought some, I am in SC so weather might be a factor (no snow to speak of). Biggest pain was the drivers side before cat, not enough room to get the socket on and the wiring harness is way up and barely noticeable, took me a while to get the harness snapped back in, a bright light is very helpful. Used an open end wrench for that one, again not too difficult, but by far the one that is most inaccessible.

 

Hey, thanks for the tips, great info. I just ordered the sensor after the cat (the one that's throwing the code) today. Are you of the same opinion as Rockledge, and that all of them should be replaced at once? Can you notice any difference in performance or fuel economy after the swap?


Ron

 

Ron, some more info to keep in mind:

The 02 sensor that is AFTER the catalytic converter is there to measure the efficiency and functionality of the cat itself. Replacing it will not affect drivability in any way. Still an important sensor, though.

On the other hand, the 02 sensors that are BEFORE the cat actually do all the work of sampling the exhaust gases and reporting back to the PCM what they find. The PCM then makes adjustments to the air/fuel mixture according to the feedback it gets from these 02 sensors.

Whatever you decide, let us know how you make out.

 

I made a mistake, the passenger side sensor was a pain. To answer your questions, I have a 'real-time' scanner and used it to look at the sensor response, I thought they looked 'slow', so I just changed all three while I was at it (I think I would have changed all three anyway, sort of like bulbs to me whenever anything is in a pair I always change as a pair). I didnt see any really nocticeable differences in fuel economy after I changed them, but the idle did seem to smooth a bit - I also disconnected the battery before I started so maybe some of what I noticed (or didnt notice) was due to resetting the PCM, hard to know.

 

UPDATE:

I've had the sensor for a few weeks and FINALLY got around to putting it in today, (been busy at work). Didn't have too much trouble with it, used an open ended wrench, and yes, I did bash my nuckles when it finally broke loose, but that's to be expected I guess...Re-set my CEL and all looks good.

Many thanks to Rockledge and JMQ for their very helpful advice.

To anybody finding this site for the first time: Definately bookmark it. It will save you time & money. These guy's are great.


Ron