Rep Power: 192

I keep getting this code like once a week for the past month and have been resetting it with scanner.

According to the sticky:
P0139 O2 Sensor Circuit Slow Response (Bank 1 Sensor 2)

Looking on Honda Parts Cheap. It appears that it might be the one after the cat?
I also don't have Vtec, didn't see an option for non-vtec version, same sensors?

After doing some research, looks like I have some options..

1) Take it out, and take a torch to it until it heats up red. Which is to burn carbon off of it?
2) Replace it.
3) Just need a software update from Honda (seems unlikely)

So, give me your options, and if I need to replace it, what brand is best?
Should add I'm 100% stock.

 
Rep Power: 235

Yes, it's the secondary sensor. If no loose connections then I would recommend replacing it as it will hurt fuel economy and may eventually lead to other problems. Not to mention it won't pass emissions. *If you have a D17A6 engine (except 2001) then you need to replace the third sensor as well.*

Also, in poorer times I've taken the sensor out and took it to the wire brush on my bench grinder and used that to carefully remove the carbon (make sure to not touch the end of the sensor with anything). *This is a temporary fix only.*

Go with OEM as these Hondas are pretty finicky when it comes to O2 sensors. Try here: http://www.hondapartscheap.com/southbay/jsp/home.jsp or get the DENSO (OEM manufacturer) here: http://www.rockauto.com/

Some are now recommending replacement of O2 sensors every 60-80K anyways to keep fuel economy as good as possible.

 
Rep Power: 192

I have a 2005. How do I know what I have?

Also, to access the 02 from after the cat, I take front bumper off, and remove bottom plastic splash shield?

Edit: Found this, it's an LX and Canadian.
http://en.wikipedia.org/wiki/Honda_D...281.7_Liter.29

Looks like I only have two sensors..Pheew.

 
Rep Power: 235

Should be able to access it by taking off the splash shield. Taking off the bumper won't help.

Also, go down to the parts store and pick up a $7 O2 sensor wrench. It makes it so much easier.

 
Rep Power: 192

Had a 02 socket in garage.

Didn't need to remove anything to access the sensors, which was nice.

Here's the downstream 02:


So I sprayed with sensor cleaner (nothing came off), took a wire wheel brush to it and heated in up with a torch a bit, sprayed again and put it back in. I'm pretty sure by cleaning the outside doesn't really do anything to improve the efficiency of the elements inside, but whatever..


Here's the upstream 02 to compare:


I noticed the upstream 02 was light gray, while the downstream was dark gray.

Took the car for a good run, felt fine. We'll see how long until the code comes back.

 
Rep Power: 192

Well this seemed to go away for a while, but came back, so I replaced with Denso plug-in sensor and it's still coming on, perhaps more frequently now.
What's my next step to diagnose the P0139?

 
Rep Power: 812

did you try cleaning the outside of the sensor too (the part not in the exhaust pipe)? if you went with a new sensor, make sure it is for the proper position. up and downstream are not the same.

 
Rep Power: 235

Check for a bad connection where the sensor plugs in and at the ECM/PCM.

 
Rep Power: 192

I didn't clean the outside of the sensor.
Yeah, I picked up a Denso 2344092 from Rock Auto it was labelled as downstream.

 
Rep Power: 192

Where would I find the PCM in a 2005?