Rep Power: 0

First, let me say thanks to everyone on this forum for their knowledge and willingness to share, it's saved me hours of frustrating troubleshooting and a lot of money.

I recently fixed a problem on my brothers 2005 Honda Civic EX Coupe and I wanted to post the solution in the hope it will help somebody out.

My brother has a 2005 Civic EX and even though it has high mileage(200K+), it was running great. He was running an errand parked the car, and when he got back in and started it up...
the Battery light on the dash was lit up, the check engine light was on, and his speedometer stopped working.

I started to troubleshoot it for him by getting the OBD-II codes from the computer, there were two: P0135 and P0141, both related to the O2 sensor heater circuit. I checked the battery, it was OK. It seemed like an electrical problem to me, I could not believe that both O2 sensors would fail at exactly the same time, but I couldn't pinpoint the problem. I got on the Internet and couple of google searches led me to this forum. I read several posting about the issues caused by "fuse #15" and they were very similar to the problems my brothers car was having. I checked the under dash fuse panel and I found that fuse #4 (a 10A fuse) was blown. The fuse panel cover listed fuse #4 as "Alternator/SP Sensor", the same circuit that was mentioned in the posts I read about fuse #15 except that on this year/model that circuit is on fuse #4. I replaced fuse #4 with a good one and it blew immediately. Based on what I had read on this forum I suspected a short circuit somewhere so I jacked the front end up, put it on jack stands and crawled under it to take a look(I wanted to inspect the exhaust manifold area because I had read that there could be issues with the wiring harness there). When I got under the car I found that the top half of the catalytic converter heat shied had broken loose and was resting on top of the aft O2 sensor wiring harness. I checked the O2 sensor wiring harness from beneath and it looked OK, however, when I checked the top of O2 sensor wiring(where the heat shield had been resting) using a mirror I found a very small spot where the insulation was missing and bare wire was exposed. I didn't have access to a welder so I secured the catalytic converter heat shield in its proper place using two 5" stainless steel hose clamps. The exposed wire was very close to the metal collar of the oxygen sensor so it was a difficult spot to get electrical tape on it. I bought a tube of high temp RTV sealant and applied a small amount to the area where the exposed wire was and then covered it with a couple of wraps of electrical tape. With the exposed wire repaired I replaced the #4 fuse with a new one and when the car was started the battery light was off, the check engine light was off, and the speedometer was working again. I don't know how long RTV and electrical tape will survive in that area but at least the problem is identified and if it crops up again he can just get the aft O2 sensor replaced. Sorry for the long-winded explanation, hopefully this level of detail will help someone out. I have before/after pictures if I can figure out how to post them

 
Rep Power: 517

Good find, thanks.

Pics can be put someplace like Photobucket. Above the text box you type in, there is an icon that looks like a postcard. Click it and paste your link in the box that pops up.

HTH

 
Rep Power: 0

I have this exact problem! I am going to check the wiring on my car tonight. Is this circuit for the front AND rear 02 sensor or just rear? Any other common places where the short might be?

Thanks for the post!