2000 Cherokee O2 sensor problem

[klimo]

Hi
I have 2000 Cherokee 115K miles 4.0L Automatic 4x4.
My check engine light is on and off from time to time.

It reads 02 sensor P138 problem. (front sensor shorted)
I have replaced O2 sensor, and cleared fault codes. Two days later problem returned. Looks like it is not sensor itself problem. It is not a constant O2 fault. I have noticed that the Powertrain computer clears codes after 4th or 5th drive cycle. (ignition on- drive- ignition off). Then a few days later it comes back for the same period, and then off again.
I just would like to know if anyone had the same problem, and maybe any possible solutions before I will start messing with the wires.

[AlohaBra]

Hey, according to the code...I just took a look at the sticky we have up at the top of the forum here....

P0138: 1/2 O2S Shorted To Voltage

That means that the wire feeding the O2 sensor has a wire crossed to the voltage feed... and is always receving feed voltage and cannot send a signal.

I would check the harness with a voltmeter...with the sensor connected.

Did you know that the o2 sensor is like a battery? It sends out a voltage ...about .5 volts when the mixture is correct. It goes lower and higher when the mixture goes rich or lean. If there is a short, it cannot do its job correctly.