I recently purchased a 98 civic ex that has a check engine light on. The computer shows up the code for the rear o2 sensor. So I changed it out, restarted the computer andstill check engine light. I ran back the wiring for the o2 sensor and about 8 inches before the o2 sensor a couple of the wires were fried.I rewired it and thelight is still on.Is there a fusein the fuse box for the 02 sensors wiring?My fuse box lid is missing and Ihave noidea what is what. Any help would be greatly appreciated.
Thanks

 

The O2 sensors are powered through the ECU. When the wires short circuited, the O2 sensor or the ECU were possibly damaged.

 

The wiring harness to the rear o2 sensor is unplugged right now and I hate having a check engine light on. This whole situation is starting to look more like a PIA. Although, the only code the computer is throwing isa bad rear o2 sensor. Is having a bad rear o2 sensor going to effect the engine long term?
Thanks again!

 

Secondary O2 isn't of immediate importance since it doesn't determine the A/F ratios, but you won't pass inspection and the light won't go off until it's fixed properly. The Secondary O2 basically is a comparison of the emissions after the Cat for the ECU to determine emissions. Trying a different ECU would be a good idea, but somehwere I thought i heard that the resistance of the wires were pretty important, so the wires might not be wired correctly. Can anyone confirm or deny that bit?

Zach

 

Zach, you are right. I didn't consider that.

Was the wire damage and repair done on the O2 sensor side or the engine side of the O2 sensor connector? If the former is true, try simply replacing the O2 sensor. If the latter is true, you may want to replace the wires.

 

The burnt wires were before the actualo2 sensor and harness. They shorted out about6 inches back before the wires go down thru the floor.I puta new 02 sensor in andcutout the bad part of the wires and hooked it back up and still there was a CIL.Does it sound likethe ECU end is bad?
Thanks!

 

What specific CEL code is the ECU throwing?

 

I don't know the exact code. I just had them scan it at autozone and the guy said the only code that came up was that the second 02 sensor is bad which is after the catalytic converter.Are there different codes that would come up up for the same problem which in this case is the 02 sensor after the cat?
Thanks again for the help!

 

AutoZone usually provides a printout indicating the code.

Here's an alternative method that you can do at home:

http://www.honda-tech.com/zerothread/1901557

When done retrieving the code, clear it to see whether or not it returns. If the CEL code doesn't return, then there may not be a problem.

 

First of all, just because the code is most likely a P0141(secondary O2 sensor), doesn't mean the sensor itself is the problem. ECU's are not that smart....yet. All that means is there is a problem somewhere in that circuit, or connecting circuits....such as wiring, ecu, connector pins, sensors. So when customers bring their car to me, and say "can't you just hook up that scanner thingy and see what it is"....it's never that easy. I would take the code and print out a diagnostic procedure(sometimes 15 pages long) and go through it all to trace down the problem. So don't let AutoZone try to sell you parts after they read the codes, they don't know what's wrong, the code doesn't tell you what's wrong, it just gives you a place to start your diagnosis. Ending rant...sorry... AutoZone is only good for chrome valve stem caps, and maybe some tire shine...

Anyways, check fuse #15 under the dash. Then get under the car and look directly over the oil filter on the back of the motor. You will see a couple big connectors with lots of wiring. Check the wires very closely as they tend to rub on the bottom of the intake manifold and short out the rear O2 causing fuse #15 to blow and CEL to come on setting that exact same code, as well as others in other cases. Actually, I think Honda came out with a bulletin on this problem, yes it is THAT common. I've seen at least 12-15 of these same problems.

Im interested to see if you have the same problem...