My CEL started coming on intermittently the other day and is now on permanently. When I was at Autozone getting a set of brake pads they plugged in their scanner and checked the error code. I can't remember what the code was (dohhhhh!!!) but the print out they gave me was as follows:

Definition
O2 sensor heater circuit low-12
Probable cause
1. - Open or short circuit condition
2. - Open fuse
3. - Failed H02S 12

Any guidance on which sensor this is, where it is located, and any easy remedies to try before replacing it? Also any ideas on cost for replacement??

Many thanks

It was probably P0031 or P0037 which is either the front or rear O2 senor.

It was probably P0031 or P0037 which is either the front or rear O2 senor.

ding ding, i agree. loss of voltage to the sensor is a maybe as well, but generally just a o2 failure.

kevin.

Is it a DIY replacement or am I better off just taking it to the dealer?

If you're under warranty, let the dealer pay for it and install it.
If not, then do it yourself.
If you can screw in a light bulb, you can screw in an O2 sensor ;)
Just need to find out if its the front or rear sensor.

It was out of warranty some time ago, so looks like it's down to me. Just finished changing out the brake pads this weekend so I think replacing the O2 sensor shouldn't be too much of a stretch.

This may be a stupid question, but where are the O2 sensors physically located?

Thanks

The rear sensor is located on your cat, if I'm not mistaken.
If it is, it can be a pain to get out. The heat might have welded it into the cat. You might want to get some nice lubes and a bolt breaker to help.

This may be a stupid question, but where are the O2 sensors physically located?

If you look under your car from the passenger side (obviously, lift you car and put it on jack stands) you'll see the exhaust piping.
The front O2 sensor is on the exhaust manifold and the rear is on the cat.
137825

Thanks for your help guys.

Is there any difference between the front and rear sensors? I've been checking out the prices of replacement units and the rear one seems to be more expensive than the front.

I've also come across "universal" sensors (without the connector) at

http://www.car-stuff.com/store/?N=11061+4294964664+1667+11921+9167

Does anyone have any experience using these? I'm curious as they are significantly cheaper than what the dealer is quoting.

I would stick with OEM if I were you...

stock front O2 cost 200 something.

if i were u , I would stick with stock

$256ish for the stock sensor - I'd still get it over the universal sensor. (http://www.trademotion.com/partlocator/index.cfm?action=getJointLocator&siteid=214264&chapter=&Sectionids=2,2496&groupid=2497&subgroupid=64754&componentid=4128&make=22&model=RX-8&year=2004&graphicID=5455230&callout=18&catalogid=2&displayCatalogid=0)

Ok, I've ordered a replacement sensor so it'll just be a case of direct plug in with no wire splicing.

I the meantime I thought I'd check out how easy the old one was going to be to get out. All that talk of breaker bars and stripped threads gave me visions of ending up screwing something up and having to replace the cat.

What a relief! It took me longer to work out how to release the catch on the electrical connector and unplug it than it did to remove the sensor guard and unscrew the sensor. Result!!!!

I had a read through the workshop manual and found the resistance that the heater circuit should be (14.1-18.9 ohms). Mine is a total open circuit. It's toast. All I need to do now is to wait for the nice man from UPS to knock at the door.

just get a test pipe and don't put the 02 back in haha

Once I install the new sensor should the CEL clear itself automatically or do I need to reset somethin?

Once I install the new sensor should the CEL clear itself automatically or do I need to reset somethin?

If you fixed the problem, the PCM will clear the CEL after 3 drive cycles.

Advance Auto Parts (http://advanceauto.know-where.com/advance-auto-parts/cgi/selection?mapx=&mapy=&mapid=US&lang=en&design=default&addr=&city=houston&region=TX%2CUS&zip=&phone=) will let you borrow an OBDII code reader with a driver's license deposit. Call first, since all stores don't have a loaner.

With the code reader, you can take a lot of guess work and waiting out of this problem by reading and clearing any CEL(s) immediately.

I recently got this same cel for the o2 sensor needing replaced. What i did before i started the replacement i disconnected the battery. Once i finished installing the part i connected the battery back which took about 25 min and after that cel didnt come back on.