Hello, i am new to this forum but have had a continuing problem with my accord. Ive done a lot of searching but cant find much to help my problem. Any help is appreciated..
I have a 99 accord ex 4 cyl 5 speed, with a ULEV motor swap..
I have the check engine light on for p0135 which is the pre cat o2 sensor.. Ive changed the o2 sensor and reset the computer and it comes back on instantly. Could this be because the ecu is for the original motor and not for an ULEV motor?
Any help in getting this Check Engine Light off would be great this orange light on my dash is driving me crazy..

 

P0135 is the heater circuit for the front O2 sensor. But it's for the non-ULEV sensor.

- Are you using a non-ULEV controller with a ULEV engine?
- Did you swap your exhasut manifold & sensor to use the non-ULEV versions of those?

 

to be honest i just bought the car about a month ago and im not sure what the previous owner has done but it looks like he half assed most of it.. i replaced the o2 sensor with one that is for the ulev motor from autozone.. could you explain better about the controller?

 

The PCM (engine computer) is very different for the ULEV engine. But I think if you have the ULEV version of the PCM it wouldn't throw P0135, it would throw the ULEV version of that error code. So because of that, I think your car originally had the non-ULEV engine, and you still have the non-ULEV PCM. Therefore, I think you need the non-ULEV oxygen sensor.

So now the big difference between the engines is the exhaust manifold. Which of the 2 pictures looks like your manifold?

 

It looks like i have the one in the second picture you have attached.. would an aftermarket header be a solution for this?

 

First, make sure you have the oxygen sensor for a NON-ULEV car. You replaced the sensor; did you get the ULEV sensor? The manifold might not be as important as the sensor.

If it's already the non-ULEV sensor, then you can check a couple things.

1) Got a multi-meter? Set it to measure resistance in ohms. Unplug the sensor & look at the wire coming from the sensor. Measure resistance between the 2 same-color (black?) wires. Should be between 10 & 40 ohms.

2) Set the meter to measure voltage. With the sensor still unplugged, start the engine. Measure voltage between the pins on the car's side of that plug, the pins that correspond to the wires you just measured on the sensor. It should have battery voltage.

Let us know what you find.

If it turns out you need the manifold, you can get a junkyard manifold if you don't want to spend for the aftermarket header.

 

Thanks, I will do this tonight when i get home and let you know what i find!

 

Resistance of the sensor heating element itself, will usually go to open-circuit if that's the problem. I'm not sure if a resistance of 41 or 42 ohms would even throw a code.

If you don't get any power coming from the car's wiring, then you'll do more troubleshooting back in that direction. Got power on the hot (+) side of that circuit? I don't remember, but a blown fuse would put out a couple other things, not just the O2 sensor. I don't remember what other circuits might be on the same fuse.

The ground (-) side of that circuit goes through the ECU, for the purpose of measuring whether the heater is working. Throwing code P0135 really means (on a basic level) that the ECU isn't seeing any current coming through the ground leg of that circuit.

 

which fuses should i check, the ones in the door panels or under the hood?

 

Drivers side underdash, #6 fuse....pretty sure you are not the SULEV but they have another in the pass side underdash #6 as well.

Step one of testing the p0135.