Hey guys, amongst other problems with this 2004 Honda Civic SE I recently got, it also has a check engine light on with the p0135 code.

I looked up the code and it's 02 heater circuit malfunction of the primary sensor, but I replaced the sensor with a good one out of my 2005 Honda Civic SE, which is basically the same car, and the code will still not go away.

It comes back as soon as I reset it. Any idea as to what this problem could be? Thanks very much.

 

first check the fuse that supplies the heater circuit (as that is what the computers looks at to determine if its a good circuit/sensor (using either voltage drop or current flow thru the sensor) ,also have seen wiring issues and also ECU damaged when the sensors fail so keep that in mind

also be aware that there are several different sensors used thru the years ,each having different resistances in the sensor heater circuit and if the incorrect calibration sensor is installed the code will flag .

 

Hey man, the fuses are fine, non of them are burnt or anything. Also, plug going into the o2 is getting 12 volts and the 02 itself is fine. I know because I have an 05 Civic and I swapped the 02s from both cars and that one is having no issues. I really don't know what it could be, but I don't think it's the 02.

 

I forgot to mention that this car has a cracked exhaust manifold, could that be the problem?

 

Re: swapping sensor from one car to another see my previous note

"also be aware that there are several different sensors used thru the years ,each having different resistances in the sensor heater circuit and if the incorrect calibration sensor is installed the code will flag "

just because it plugs in doesnt mean it is correct for that year.....

RE: the cracked manifold will not cause this code you are getting ,it might cause a lean code (different "P" code number), but not a O2 heater code .

 

Hi, but wouldn't it flag in my 2005 Honda Civic then? What I did was basically take the 02 from my 2004 Honda Civic and swapped it with the one in my 2005 Honda Civic. I basically exchanged them and my 2005 is not throwing any codes. So if the sensor was incorrect, wouldn't my 2005 throw a code as well, or no?

I see what you mean. The manifold as a pretty big crack in it and I thought that might be the cause of the 02 not heating up quickly enough. That doesn't sound plausible, does it?

 

" but wouldn't it flag in my 2005 Honda Civic then"

not necessarily it depends on what the ECU control/test limits are and if the sensor falls within those test limits . didnt realize you had done this swap(this can be dangerous as i mentioned failing sensors can damage the ECU so if it was bad you could have damaged ECU in both cars ) and so would think its probably indicating its ok (how long have you driven the 05? how many drive cycles ?) in which case since the 05 isnt flagging a heater code with the 04 sensor it would indicate a wiring or ECU problem in the 04

yea cracked manifold wont cause O2 heating issue this is what the heater in the O2 is for .

 

I doubt a failing sensor can damage the ECU, no? Sensors are known to fail regularly and many people do not repair them right away. And it might be a wiring issue like you're saying. Maybe it is the ECU? Do you think I should swap them and see? Are they interchangeable? Thanks.

 

Hey bro, I fixed it! It was the option fuse! For some reason it was missing! It caused 2 major issues, this one and my DRL lights went out. Thanks a lot for your help, appreciate it!