KingstonJeep

Does it make sense that the two prongs in the wiring harness that go to my upstream O2 sensor heater read 13.9V when the engine is running? This is the engine side of the harness, not the O2 sensor side.

Based on my understanding of the system I would've thought that there should be 0V at the prongs on the engine side. The only power the prongs should get is what the O2 sensors generate once they warm to 600F. Once the sensors get to that temp, they send a signal ranging from 0.1V to 1V to the ECM.

Other things are behaving normally. The power going to the sensor heaters from the engine side is 1.67 V. The resistance between the two heater wires on the O2 sensor side is about 6.7. I didn't bring the engine to temp and check voltage output from the sensors because there are issues with the engine right now. I'm trying to figure out if the 13.9 V is normal or malfunctioning behaviour. My brain is getting tired thinking about this, but it seems like what it's saying is that effectively the ECM is getting a signal of 13.9 V from what it thinks would be the upstream O2 sensor?

robsjeep

there are at least two types of oxygen sensors. the Early Renix Engined XJs as my 1990 is, use a resistive sensor, which does not generate a voltage, rather it gives a changing resistance.

see link...
https://www.dubizzle.com/blog/cars/t...xygen-sensors/

Some of the early jeep like mine use the resistive type, a "Titania" sensor,

Most cars use the "Zirconia" sensor, which generates a voltage.


You may have the Titania type of system, Is your Jeep Renix motored? If so, the jeep brain sends a voltage across to find the resistance value of the sensor, I believe the brain compares the voltage drop across the sensor to a reference value, and from that infers the oxygen content, resistance varies with Oxygen content.

The Zirconia type, which is most common with generate a voltage verses oxygen content, and as such there should be no voltage being supplied to the sensor ( except power supplied to heated sensors) late jeeps have this common type, my buddy has a 2001 xj with this zirconia type that generates a voltage

I think you have the early Renix type. what year and model?

cruiser54

What year is it?