Fuelly Forums - So I measured my o2 readouts on the new VX..

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So I measured my o2 readouts on the new VX..

and I'm not sure what to make of it.

at cold, i e a -0.8v readout

at idle after warmup between +.25v and +.3v

whats strange, when just maintaining 60mph w/ hardly any throttle, i get between +.93v and +1.05v

when slightly accelerating while already at 60, the readout goes to -.25v to -.29v

am i missing something here? i measured the readout just as described with pins d14(+) and d16(-). the numbers are nowhere close to what is supposed to readout. does this mean the o2 sensor is indeed shot and would hopefully explain the 40mpg mileage ive gotten so far

Here's what Krousdb had posted about his experience:

Quote:

Originally Posted by Krousdb

Connect the positive lead to D14 and the negative lead to D16. This will give you positive readings above stoich and negative readings below stoich. When the O2 is not warmed up, you will see a constant -0.8 reading. When the engine coolant and O2 are up to operating temp, you should see the reading spike to +0.4. At that point you will feel that it takes an exaggerated amount of throttle position opening to accelerate.
<snip>
While observing the O2 output what would be an indication of being in lean burn mode? Well according to Dax's OBD training manual, a rich condition would yield a negative voltage, as much as -1.3V in very rich condition. A lean condition caused by disconnecting one injector would be positive 0.6V. So positive values approximating 0.6V would be a good indicator of a properly functioning lean burn condition.

From what is said, it seems to be working, but you're getting into a super lean condition though. I'd PM Krousdb to see what sort of readings he got as I haven't hooked mine up yet.

Quote:

Originally Posted by NickF829

Cold and idle readings are good. When entering lean burn you will feel a sudden loss of power and the DVM will read 0.4-0.45. It sounds to me that the O2 sensor is bad, but I don't know for sure. My bad O2 sensor was just stuck at -0.8 and never moved.

Well just to add to this I just hooked up my dvm and I am getting similar readings except the lean burn readings for me are .79 to .85. I am assuming that we get different readings because of every o2 sensor is a little different, I say that because although its a 5-wire sensor there are 2 more wires that go to a calibration resistor that is special for each o2 sensor... Or i could be completely off base and it could be any one of a million different things wrong with our cars(different fuel pressure, clogged injectors, slightly different ignition settings, ect........) Hope this helps :)

There could be a contributing factor of elevation difference as well.

As a side note, how were you both hooking up your DVM/DMM? I was thinking of just getting a spare set of leads and soldering them into the respective wires near the ECU.

yep, I cut a spare set of leads off my meter and soldered them into d14 for the positive lead and d16 for the negitive lead... I also got backlight dvm and velcroed it to my dash, now all i have to do is to convert the cars battery voltage to 9v and wire it into my meter so I won't have to replace the battery in the meter.....;)

update... I put in a brand new o2 sensor and now my readings are +.6 to +.7 volts when in lean burn. the readings are lower than the old sensor(old sensor +.79 to +.85 volts) I haven't noticed any gas mileage increase with the new sensor...

what mpg were you getting before you replaced the o2?

NickF829: Since I'm not running a VX, currently, I cannot comment based on direct experience. In looking at your numbers and in consideration of how my standard O2 sensor behave, I think your looking at a circumstance where you have some other sensor which is either not working entirely correct, or something. In any case, your readings, relatively, make me belive your not actually getting into lean burn, which means the ecu is thinking something else isn't Ok, for lean burn.

fyi I was getting between 44 - 50 mpg and its the same with the new sensor....