Hector,
That looks like it would be a .99v reading on a normal sensor (2.5v offset + .99v reading = 3.49V). That points again to the need to block the 2.5V offset voltage and be able to use the stock sensor(s) on a normal .1 to 1.0 volt A/F Gauge.
I don't knopw if it is worth going after or not. Mopar Performance has said that they will be introducing some gauges soon. They will probably be Autometer, just like the SRT-4 boost gauge.
If Mopar says we have to use another O2 sensor to run their A/F Gauge, then I guess there is not much use in trying to get a usable signal form the stock O2 sensor (wideband, heated and 2.5v offset). On the other hand, if the Mopar Gauge is capable of using the 2.5v offset signal, there will be happy days in the aftermarket.
I still think there may be some merit in the blocking of the 2.5V signal. If you were able to take a reading, and it was near the 1v level at WOT and 90% duty cycle, that in itself says that the signal is strong enough that it could stand a blocking device.
If you want to chance it, put a diode in series with pin 3 (sensor return; what we would normally consider sensor ground - at any rate, it is the "ground" reference for the sensor signal and carries the 2.5v offset)and then check the voltage again.
You can check the voltage before starting the engine. If it reads 1.8V to 2.8v with key on and engine off, reverse the direction of the dioode and try it again.
If you then see .9 to 1.0 (volt range for normal sensor) volts measured under the same conditions, start the engine and carefully check to see if the signal measures accurate as compared to what you saw before. After a slow run-up, and no errors, you could give it a try at the conditions you used above. By this I mean if you would normally be seeing 1.0v on WOT and 90% duty cycle, and you saw 3.49 without the diode, you would be seeing .99v now. If this works, and doesn't cause any MIL to illuminate, all you would have to do to market it would be get the connectors (one male and one female) for the stock O2 sensor and make a Y connector. The center of the Y would go to the sensor, one leg would go upstream to the PCM - via the other connector (no wiring harness cut) and have no mod to the wiring. The other leg would have the diode in line with the sensor return and enough heat resistant wire that a normal butt connector could be used in the engine compartment; away from the extreme heat near the sensor.
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