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Old 05-06-2008, 11:31 PM   #1 (permalink)
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Perhaps honda specific: Will a code 41 (o2 sensor heater) tank my mileage?

Based on the way the car runs/idles I'd say the o2 sensor heater code isn't affecting my fuel mapping, but then you never know, any ideas? Wanna know how much effort I should put into fixing it tomorrow.

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Old 05-07-2008, 01:39 AM   #2 (permalink)
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Probably not. IME, heated oxygen sensors are just to make sure the cat's up to temperature and if it's not richen the mixture until it is.. It shouldn't impact your A/F ratio enough to do much to mileage.
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Old 05-07-2008, 01:53 AM   #3 (permalink)
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The thing is, I think it's because of an old wiring trick I did to make my ecu (which wanted a 4-wire o2) accept a 1-wire o2. Now that I have the right 1-wire o2 ecu in there it's throwing the code...
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Old 05-07-2008, 03:31 AM   #4 (permalink)
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What did you do to the wiring, and is there a change you mussed up your oxygen sensor? Too rich and it'll supposedly get sooty... Once I leaned out the AFM on the Camry to get rid of the obscenely rich A/F ratio, my rear bank oxygen sensor CEL turned off and hasn't come back on since.
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Old 05-07-2008, 09:00 AM   #5 (permalink)
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Well, I recall doing some trick to bypass the heater so the ecu didn't throw a CEL, or mehbe I just turned the heater off on the chip I used, but I just went out and looked and it appear the heater wire is cut, so I'm going to hook that back up, poke around, and if it doesn't work, I'll forget about it until I get home from school.
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Old 05-07-2008, 09:11 AM   #6 (permalink)
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My tracker has the O2 sensor heater code as well, from what I've read this is only important to get the sensor up to temp faster when the engine is cold. After the exhaust manifold gets warmed up (maybe 1 min) then the "heater" isn't important.
I have a scangauge and my tracker runs in "closed loop" mode all the time and I'm getting good mileage so I've decided not to bother replacing the sensor, the fact the GM stealership wanted $470, and suzuki wanted $320 for it also influenced my decision...

If the sensor fails completely then the motor will go into "open loop" and burn way more gas, maybe overheat the cat, and generally run bad. Then its time to get a new O2 sensor.
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Old 05-07-2008, 09:16 AM   #7 (permalink)
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Quote:
Once I leaned out the AFM on the Camry to get rid of the obscenely rich A/F ratio, my rear bank oxygen sensor CEL turned off and hasn't come back on since.
roflwaffle, I am curious how you leaned out the engine? Its something I'd like to try.
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Old 05-07-2008, 10:08 AM   #8 (permalink)
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Yes, it will affect MPG, it will not go in to closed loop (or is it open?) as fast. The ECU will throw extra fuel until the O2 sensor comes to temp. I don't know how much longer it will take/ how much extra fuel the Honda throws at the car to prevent driveability issues on warm up.
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Old 05-07-2008, 11:05 AM   #9 (permalink)
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I just did some more reading on O2 sensors, to summarize:

Heated O2 sensors allow the sensor to be used for readings more quickly and allow the O2 sensor to be placed farther downstream in cooler locations in the exhaust.
Testing unheated O2 sensors requires the engine to be run at 2500rpm or so to provide a load to create enough heat so they work.

So, based on this, I would think that you are OK using an O2 sensor with a broken heater unless you;

like to warm up your car in the winter by letting it idle for 10 min,

or, have a huge engine running at very low load most of the time.

I'll assume neither of these conditions is true for you or your honda, the only other condtion would be idling in stop and go traffic for a long time. This may allow the exhaust system to cool enough so that an unheated O2 sensor would cool to much but I doubt it, maybe at -20.

That all said, if someone gave me a good O2 sensor I would like to try it out and see if there is any difference in my mileage, as I didn't find anyone else reporting about running with a failed O2 heater. I do have to think that since my car is running in closed loop mode that the sensor is reading within the normal range once the sensor is warm and that since I don't idle the sensor gets warmed up quickly enough not to worry about it.
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Old 05-07-2008, 11:24 AM   #10 (permalink)
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This has nothing to do with the cat. The sensor needs to be hot to generate a signal. Exhaust heat will eventually heat the sensor up. The heater just accelerates this process and lets your car go into closed loop mode sooner.

I had this problem temporarily after I installed my Bosch gauge. The AEM gauge it came with was responsible for heating up the sensor, so I only used one wire on the old harness for narrowband emulation. To keep the ECU from throwing heater circuit codes, I chopped the harness off the narrowband sensor and soldered a 10 ohm resistor between the heater wires. Make sure it's rated for at least 10 watts though, or it will burn up. Also keep it clear of your wiring/looming, or it could melt them. Alternatively, you could wire a brake light bulb and socket in there to keep the ECU happy, if you don't mind your engine bay glowing for a few seconds on each start.

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