Eighty5TransAm

My car has been throwing me a code 44 (O2 sensor lean) and my car is running rich. I hooked it up to a voltometer, and got .336V. On the facts page, it says the voltage should be between .850 and .900 at WOT, and the lowest should be .300. Does this mean my sensor is bad, I just replaced it a month ago.

Thanks, Curtis

8Mike9

It sure seems as if the O2 sensor is at fault, but you may have another issue running rich...or it may just be that the O2 sensor is bad, and the fuel is dumping in to try and get a good O2 reading.

I'd disconnect the battery to give time for the ECM to clear out, replace the O2 sensor and monitor the voltage again, if the mv's are staying high, then look into why it's running rich.

GMTech

Actually, 300mV is NOT the minumum. It is not uncommon for it to go below 100mV, providing it does not stay there. It should rapidly fluctuate between 100-900 mV, several times a second (your DVOM may not be able to read it this fast).

Disconnect your O2 sensor, and measure the voltage on the ECM half on the connector. You should have 450 mV. This is the "bias" voltage applied by the ECM. If you don't have 450mV +/- 25mV, then you probably have ECM issues. If you do, Then you need to MAKE ABSOLUTELY SURE that you aren't running lean. After all, why shoot the messenger? Its only doing its job by telling you, that you are running lean. Make sure the Fuel Pressure is up to par, no vacuum leaks, etc...

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rhuarc30

One other thing to check, your 02 sensor could show rich if you are getting incomplete combustion for some reason, say worn plugs or wires, etc. Also check your tps, and one time I had a rich condition, turned out my darn air filter was just so clogged that it was barely letting air through at all.
Always check the easy stuff first
John

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