O2 sensor??

[superfiveo]

I have a 89 4.0L I have been testing all the sensors today and all seem to be ok according to the Chiltons manual exept the O2. It say's the voltage should be fluctuating .40 and .06. Mine tests about 4.8 to 5 volts. Is this possible?

 

[XJNick]

The only way that's possible is if the sensor has a dead short or your reading the wrong wires.

The Jeep's ECU sends out a constant ~5 volts to most of the sensors (including the 02) and then interprets a condition based on the amount of voltage it recieves back on a third wire.

-Nick :!:

 

[superfiveo]

man i'm stupid!!!

 

[superfiveo]

I had a bad sensor. Found a used one and put it on and tested it and I had voltage out of the signal wire. I could not get a voltage reading out of the old one.

 

[XJNick]

Glad it was a simple fix :mrgreen:

-Nick :!:

 

[superfiveo]

well, i have a new problem. The ~5 volts going to the o2 sensor is not a steady 5 volts. It changes between 2 to 5 volts.

 

[XJNick]

It changes between 2 to 5 volts.

Sounds like the output wire of the sensor's variable resistor

-Nick :!: