1point7db2

So ever since I've had my coupe its thrown a code 41 (02 sensor heater circuit) I figure ok, I need a new sensor. I check the bad sensor with a multimeter and sure enough its out of spec. I throw in a brand new sensor today and it still throws code 41. I commute to work, and im getting like 220-250 miles to a tank on the highway. I assume the car is running in open-loop. I still have vtec, but sometimes I noticed that my rev-limiter fluctuates. One day it was at like 5,500, then 6,200 today it feels like being at 6,800 wtf? I dont know if that is related to the o2 or what. So what do I need to check next? Do I need do get some diagrams and start going through some wiring?

mwieczorek43

I don't really have anything good for you...

I ran w/ a code 41 for nearly 6 months and never had any of your described issues. I had slight power loss in the low-end every once-in-a-while, but never had a goofy rev-limiter. I also ran lean when the engine was cold. I think you might have something else going on...

I know this is a silly question, but are you sure that's your only code? Also, what brand o2 did you buy?

1point7db2

Its a denso o2. Code 41 is the only code im throwing now, last week I got 22 (vtec press.), but I cleaned out my vtec selenoid and that cleared the code. I went out a couple of minutes ago and checked supply voltage to the o2 heater, and it is receiving 12.2 volts with the key on. I dont know what else to do.
I dont know why else I would be getting this kind of mileage, I dont rag on my car all day, I might hit vtec like 4-5 times a week. I've got a short-ram, and 2.25 piping back to a Tanabe muffler. Those are the only mods.

mwieczorek43

I used a NTK (ngk's sensor division)...
My mpg went down quite a bit for the first week or two. But then started getting better and better. Now it's like it was before. I don't know if these things get 'broken-in' or what? But I was suprised when it started improving over time.

1point7db2

I went through some diagrams... The orange/black wire coming out of the sensor goes back to the ECU to pin A6. The wire reads 12.5 volts at the ecu. WTF, I cant find a break in the circuit anywhere, the heater gets voltage, and it comes back out and sends voltage to the ecu. But is it the correct voltage? Cant find anything on what the voltage should be at the ecu. I know it should be 12 going into the sensor though. This is really pissin me off now.lol

1point7db2

Ok I figured it out- it was my ECU. Installed another P28 and code vanished, ill fill up tommarow, but I can already tell the difference in fuel mileage from driven around town today.