Tronixx

Anyone ever get this code with a check engine light? I have an '04 EX with less than 50K. Makes me mad that something is already wrong with the O2 sensor, and is a $250 part.

Anyway I've read that I may not necessarily need to replace it - I've been through this before with other cars - and the guy at Autozone told me it may be a bad wire but that the wire or connection might be "burned out" within the sensor so the only way to fix it is to replace the sensor. I've already inspected the wires and connnection, can't tell anything from my point of view.

My question is how can you tell if it is something else in the wiring or if there is a short somewhere. Its easy to say to check the wiring but how much can you actually do and how? Is there something in particular that causes this malfunction? I did put in a K&N intake earlier this year but that is the only thing I've really messed beneath the hood besides oil changes. And I didn't get this light to come on right after service, just happened all of a sudden, it did start to get cold out lately before it came on.

Is replacing the sensor an easy job, I don't have a very rusted out connection or anything, but I remember this same thing was very difficult on my old CRX. Is this something best left to the dealer or a shop somewhere? Is there any special tricks with getting rid of this type of code that anyone knows of?

streetglower

iTrader: (13)

yes there is more to a visual inspection of wires which is always the first think to do.

with a digital multimeter, you can test the wiring for resistance, voltage, continuity, etc... if you were to test the sensor for voltage, there are 2 pins on the o2 sensor that will give you a voltage reading, I believe it is .1V-.9V.
basically lean, rich, lean, rich, etc... you can also test the resistance of the heater circuit within the sensor itself. you can also check the continuity of wires to make sure there is no break anywhere. in the manaul it gives exact pins and locations to test, but if everything looks ok, more then likely the sensor is at fault. if the light comes back on afterwards, then there is another issue.

and it is very easy to replace the sensor. with a wrench or o2 sensor socket will do the job. just loosens the old sensor, disconnect it and replace it.

Tronixx

thanks man - excellent info

Axe Man

iTrader: (1)

P0135 is defined as a problem with the O2 sensor heater circuit. Not the O2 sensor function itself.

OBD-II O2 sensors are 4 wire. 2 wires are the sensor itself which controls the A/F mixture. The other 2 wires are a heater circuit which comes on when the engine is cold to warm up the sensor rapidly. A "cold" O2 sensor cannot monitor A/F mixture which is why this additional circuit is there.

You can check to see if the heater in the O2 sensor has failed fairly quickly. Unplug the sensor from the wiring harness. With an ohm meter measure the resistance across the 2 white wires. It should measure almost a short and most likely under 1 ohm. If you get no reading or high resistance the heater circuit has indeed failed and you need a new O2 sensor. If it reads almost a short the sensor is not at fault and there's a problem in the wiring harness.

I have the wiring diagram if you need it. E-mail me at mjats@juno.com if you want it.

Tronixx

sweet - yeah that makes perfect sense. So I guess my issue is only when the car is cold, so it really doesn't sound like a big deal, but I just want to get that stupid light off in my dash.

Someone said there was no more "tech" left on this board, but you guys proved that wrong. Thanks for the help!

Boilermaker1

iTrader: (16)

O2 sensors are not $250 unless they went to widebands at some point without telling anyone. Both O2s are $43.75 from majestic honda. Buy local, they might be 80. Just change it, you're supposed to change them every 60K for best efficiency anyways.

Axe Man

iTrader: (1)

Some additional pointers: The O2 sensor with the heater fault is the first one on the exhaust manifold before the cat. If you measure the white wires and you're still unsure if it's good or not go to the O2 sensor after the cat and measure it's heater wires. They should read the same and you know the second O2 sensor is good. So you can use it as a double check.

Yea, the heater circuit only comes into play when the engine is cold. When an engine is first started it is in what's called "open loop" and the ECU controls A/F without input from the O2 sensors. But emissions regs require that an engine must get into "closed loop" as quickly as possible. So a heater is used in the O2 sensor to heat it up so it functions. The ECU then checks the O2 sensor. If it hasn't heated up and provide good data the ECU then flags this trouble code. But once the O2 sensor heats up via the exhaust heat it will function fine. So yes....it's only an issue between fully cold and normal operating temperature.

donperry

I have this same problem with my car. I Have a deleted cat i'm not sure if that could casue "heater circuit malfuntion"

gearbox

iTrader: (95)

deleted cat shouldnt matter. heater circuit in the primary sensor should have nothing to do with the cat. usually it simply means the heating element has failed or the wiring is bad going to the sensor. make sure you get the right sensor and that its 'oem type' with the plugin connector. 01-03 uses cheap narrowband, 04-05 uses expensive wideband.

donperry

Thanks Gearbox. U always helpful

Odelay12v

2000 Civic Lx 154kmiles ...OK so i just replaced the Upstream or the one between the cat and the exhauset man.. And the light still has now come back on after only 24 hours... Any ideas? I get the same code too P0135 O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 1). This isnt the first time i have replaced O2 sensors but first time on this this Honda..

michigan98gt

I am having the same issue. Replaced front sensor and reset ECU and light is still on.

DjDisturbed

I'm having the same issue , I just replaced the upstream O2 sensor and the light is staying on. I drove the car for about 20 minutes on the highway and still did not go off.
I see that other people are having the same problem.
I'm going to drive the car a few more days and if the light stays on. I will check to see what code it is showing. If it is the same code what do I do then ???

jucamvil

Hi guys.

I’m writing from Bogota, Colombia

I have the same problem. I replaced my o2 sensor based on this and other forums. Replace part was NTK 24289 but It didn’t work. When car is cold, engine light is on and when car is hot light is off.
I also reset the ECU.
Do you know what is EXACTLY the part number to replace my stock o2 sensor?
I saw that new sensor has a BLUE cable and my stock was GREEN.

Thanks

Seth Diringer

My engine light came on. I got a P0135 "cracked exhaust manifold, lean mixture" for my 2001 Civic LX. I changed the cracked exhaust manifold with an aftermarket part ($250 plus shipping, extra gaskets & bolts and an O2 sensor wrench; about $350 total. Factory part: $900). I still got an P0135 "HO2S-11 (Bank 1 Sensor 1) Heater Circuit Malfunction". That's the front (pre-cat) O2 sensor. The engine light was still on all the time, the car worked fine.
I phoned around for an O2 Sensor, got $170 as quotes, then one dealer had a $58 O2 sensor from Bosch, already threaded for Honda. It's the "Bosch Premium Oxygen Sensor", Part 15710. After an ECU reset, the engine light has not come on again so far. I'm cautiously optimistic. Note: these are Canadian prices, it will be cheaper in the US.

MatthewMan

https://www.rockauto.com/en/catalog/...2)+sensor,5132