tide55

I have a 2004 Honda Civic EX. I noticed recently the engine light would come on and then go off later on, but now it's staying on. The problem is the oxygen sensor (or airflow AF sensor?) in bank 1 sensor 1, which from what I understand by reading this site is the sensor before the catalytic converter.

The codes I receive are:
P0135: O2 Sensor Heater Circuit (Bank 1 Sensor 1)
P0134: O2 Sensor Circuit No Activity Detected (Bank 1 Sensor 1)

Would freeze frame data help here? Could I monitor the O2 sensor live and would that offer any good way to diagnose?

What I really need I think is a good how-to step-by-step on testing the sensor. Also any tools I might need.

And could someone explain to me why our cars apparently have a "wideband" sensor that is much more expensive to replace? I found this $35 before-cat sensor that supposedly works on 1986-2012 Civics... but that can't be right can it?

Thanks

lowlife9

really there only good for 60,000 miles then they start to get dirty and clogged reducing MPG even if you don't get a code. whatever you do do not purchase an off brand or universal sensor only purchase oem replacement DENSO or NTK you can usually find them cheaper at advanced auto search around. i repeat only buy DENSO or NTK.

ezone

Wow. I can't even......Wow. No. Don't....Just... NO.

Whichever brand was originally installed from the factory is best. Look on the original sensor, it should be stamped somewhere on it.

cja3455

The sensor signal can be read via the obd2 port but since you are getting a code of no sensor activity then you won't be able to read anything. The wideband AF sensors are only in the 04-05 models and they perform better then the regular ones. I used a Bosch sensor when I replaced mine and immediately felt significant improvement in throttle response, more then the improvements of air intake and exhaust combined. These are some important devices when u replace the sensor make sure you don't touch the head. It's relatively easy to replace all you need is a sensor socket and it's easier to get at it from under the car

tide55

Thanks guys. Are you aware of a good how to on testing the existing sensor?

Would you mind sharing the model numbers of the ones you guys are using and how much you paid?

ezone

I let the computer be the judge.

lowlife9

i would never use a bosch sensor in a honda. the autozone guy ordered the wrong sensor and tried to give me a more expensive bosch sensor at no extra cost. i politely declined his offer and decided to wait for the oem denso. he told me he would have done the same. the part number was 234-9005 denso. i believe i got it on sale for $90-$100 dollars at the time.

tide55

Update on this. The heating element in the old sensor was bad. I got some help from ezone in a different thread here. I ended up buying an ACDelco part from amazon. I ended up paying $100 after tax. Here is the part:


For about $20-30 more has a lot of positive reviews since apparently it's Honda OEM.

The Denso 234-9005 is the wrong part for a 2004 Civic EX. Even though auto parts suppliers like Amazon say it fits the EX model it does not. I checked Denso's website after reading some wrong part reviews on the internet. The right Denso part number for the Civic 2004 EX is 234-9017. It was too expensive for me at the time although I checked just now and .

Thanks to everyone for their help