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Hello everyone, newb here-
I already did a search on here and really couldn't find anything concrete. Its a long story but I have a 2003 civic Ex coupe that now has a 2004 civic Ex ECU. Vehicle runs fine except for the fact that it throws the check engine light with code P0135 (Primary o2 sensor heater circuit malfunction). My understanding is that the 2003 has a narrow band o2 sensor but the 04's use a wide band A/F ratio meter. Apparently the ECU is looking for different inputs from the sensor? Questions: Is there a quick fix for this? Would the 04 sensor (more expensive) plug into the 03 harness and should that take care of the problem? Is there something I can do with resistors or relays to trick the ECU into seeing the correct inputs?

I appreciate anyones help with this and thanks in advance.

 
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Anyone??

 
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you cannot use an 04 primary sensor in an 03 and vice versa, but since you are using the 04 ecu, you should be able to use an 04 sensor without issue. the pinouts are the same on the cable, but the sensor is differnt so the return voltages are different. i have an 03 sensor if you need one. and i'll sell it cheap, i can't use it. i tried had it in the car for 3 days, code kept coming back. spent the 300 bones on the "correct" sensor and presto, code gone.

my question is why are you running an 04 ecu in your 03?

 
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Tuning-
Thanks for the reply.

Again, it's a long story but basically we got the car with no ECU and an '04 ECU was the first one that we could get our hands on.

This is all helping me get to the bottom of my problem. I'm just not sure why you would offer me an '03 sensor when that is the obvious root of the problem?? I have an '03 civic Ex with an '04 EX ECU. When we first got the car going the CEL came on and I figured the sensor was the problem so I replaced the original '03 o2 sensor with what was sold to me as an '04 wideband sensor but the car kept throwing code P0135 (heater circuit malfunction). Now your saying that the pin out is the same on '03 and '04 so by replacing the sensor the light should have cleared and made the ECU happy. It may be possible that what I was sold is in fact an '03 sensor?

Can someone tell me what voltages I could expect from an '04 a/f ratio sensor, both the output from the sensor and also the resistance on the heater side of the sensor?

Thanks!

 
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i'd figure it'd be pretty easy to get an 03 ecu. but what i meant is that the pinouts for the vehicle harness are the same and go to the same pins at the ecu. the sensor itself however has different values. i'm no home at the moment so i can't tell you what voltages/resistance you should be seeing, but i'm pretty sure i have a thread here somewhere with the different part numbers....nope, couldn't find it.

i'll take a look at the part numbers once i get home on saturday.

 
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Tuning-
Thanks again for taking the time to respond. I have a boat load of '03 sensors and apparently, I may have one installed in the car as we speak!? I would really appreciate it if you or anyone else can give me the values that I need to look for on the '04 sensor.

 
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Values anyone????

 
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Hey, I was reading elsewhere that the narrow band o2 sensor in 01-03 civics puts out 0 ~ 1 volts, where the wide band o2 in a 04/05 put out between 0 ~ 5 volts. i could be wrong but those could be your numbers.

 
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Um you could just get the wideband sensor. couldn't you just clip the harness off of the 03 sensor and solder them together and use that sensor? Besides why wouldn't you want the wideband? widebands are way better.