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Hello all,
I own a 95 GSX and the check engine light recently came on. I took it to Mitsubishi and for no charge they told me the light was on because of a malfunctioning O2 sensor(on the manifold...positive.) I also began to get very crappy mileage. I live in Southern California, where the cheapest 92 octane costs $1.95 aa gallon, and upwards to $2.35. My question is, since i know there is a reading going into the ecu from that O2 sensor(way less than .88-.92 volts, actually .068 on occasion and it does fluctuate), is it possible that my crummy mileage is because the ecu receives a signal way way way less than anywhere around .9 volts...it thinks the car is running too lean and automatically dumps in as much fuel as possible to compensate? I get 10-13 mpg probably but do boost 1/5 of the time. Thanx!!!
 

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While, we are on the subject, does anyone know if there is a way to actually test the O2 sensor. My original O2 sensor went bad on me because the code was saying that something is wrong with the temperature of my o2 sensor. This was done on a computer with ODBC software. I've since then replace it with an after market one. Still, I getting the same code. I'm also getting pretty crappy mileage as well. If anyone knows how to check the o2 sensor when taken out, please let me know.
 

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Well, I'll tell you what I do know... On a 1gen the O2 sensor heater should have 12 ohms across terminals 3 and 4 of the sensor side of the harness @ 68 degrees F. And on the harness side of the connector you should see battery voltage on terminal 3. Also, on the O2 sensor heater ground circuit: if you connect the leads to terminals 2 and 4, in turn, and ground, you should have continuity.
After engine is warmed up, at idle I believe you wanna see .4 volts and at higher rpm's you should see it increase to .5-1.0 volts. If the ECU sees less than .45 volts after it's warmed up and above 1,500 rpm's then the ECU will set a code 11 and go into an open-loop mode where it uses a default value instead of sensor feedback. Knowing the factory's penchance for things to be rich; this should bring about crappy mileage, performance and the like. Hope this helps somebody, and if I'm wrong somewhere, somebody tell me.

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Rocky Mountain
'91 Talon Tsi AWD
 
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