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Old 12-27-2006, 04:26 PM   #11
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Originally Posted by NickF829
what is a DVM? Would a o2 sensor trip a check engine light?

Thanks for the welcome, I definately have been checking out the site, and can't wait to start upping my mileage
You can get a inexpensive, but functional DVM from Harbor Freight, for a very small amount. They put them on sale, fairly regularly, for $4 or so.

On my 89 Honda, I changed the O2 sensor from a single wire unit to a 4 wire unit. Fundamentally, the signal isn't any different, but the 4 wire unit heats up electrically, so it's fully functional within about 2 blocks of driving, where the 1 wire has to wait to get heated by the exhaust. At the same time, I wired the sensor so I could hook a DVM to it. I set it to the 2 Volt range, DC. It typically cycles between about 0.75v and 0.25v, every couple of seconds, when the ecu is using the sensor to adjust the fuel mixture.

On your car, it should have a 5 wire sensor, which is essentially a specialized, enhanced range unit. From what I've read, the unit functions similar to a normal O2 sensor, but it's range and the voltage it put's out is different. I would quote what you should see, but since I don't have one, I could just steer you astray.

On the ECU, check engine light, it is constantly watching the O2 sensor and trying to adjust the fuel input. However, your ECU also watch's for a specific set of conditions to exist, which then allow it to go into lean burn mode, which is why your car has the 5 wire sensor. The ECU would only throw an actual fault, if it appeared to the ECU the sensor had failed 100%. My thought was that somehow the ECU wasn't getting as good information from the O2 sensor as it would normally, making it bad enough not to go into lean burn, but not bad enough to throw a fault code.

Great choice for a ultimate economical driving vehicle, IMO!

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Old 12-28-2006, 04:59 AM   #12
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wait wait, you are getting a check engine light? if so its really easy to diagnose.

don't waste your time or time will waste you
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Old 12-28-2006, 12:27 PM   #13
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no, no CEL is on, I asked because I thought I would know an o2 sensor was bad because it'd throw a CEL which i don't have, but now that I realize a o2 can be on the fritz before it actually "fails" enough to trip the CEL

i picked up a DVM today, how do I check the o2 sensor with it?
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Old 01-03-2007, 06:27 PM   #14
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my gas mileage went down a fair amount a tank or two before my o2 sensor went.
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Old 01-03-2007, 07:30 PM   #15
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the local honda dealer mecanic told me that the ecu doesn't normaly pick up that the o2 sensor isn't working unless it's compleatly burnt out, if the o2 sensor is sending any sort of singnal at all, the ecu thinks it's still good.
you should get more then 40mpg, but if you do all highway driving, expect high 40's maybe 50mpg unless you can find some really good low roling resistance tires, make it a bit more arodinamic (search around for belly pan info, grill blocks, and wheel skirts), also it's hard to find the stock 165/70-13" tires, so most people replace them with 175/70-13" tires, and those tires are 10mm wider, going with something narrower like 155/80-13" would be a better choice, over time it's all kinds of little things like that, that will add up and bring you down.

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