I have a 2002 Jeep Grand Charokee with the 4.0 in it. I had problems with it overheating and took the advice of the following link and put a mechincal fan in it. http://www.justanswer.com/jeep/3bq8r...n-not-mov.html

The overheating has stopped but I am still getting codes that the O2 sensors are throughing.

I have replaced all the O2 sensors and was worndering if the fan relay connects back to the computer? If so is there a way to have the fan relay send the correct response back to the computer so the computer sees the fan relay working as it was entended thus shutting off the O2 codes it is sending?

I am still lost on what to do and would like any type advise anyone can give...

What kind of o2's did you use? I always recommend OEM ones. It sounds like it could be something other than the o2's. What is the specific issue when you pull codes? o2 sensor voltage irregular?

OEM ones, I have a bad habbit of reading prior to doing anything to my cars and from a few people in different fourms stated a few different types of O2's where giving issues.
When I hook my ODB to it I see regular sensor voltage to each of the sensors which is what is making me think that it is the coolant relay. When I got the Jeep the man that owned it before me cut the wires that hooked the fan to the relay and hard wired the fan. After about 6 months the fan started getting weak and the engine started overheating. After reading about the cost of replacing the fan and rewiring it back to the origonal my pocket book decided it would be better for me to put a machinacl fan on it and stop the overheating. This car is not driven more then about 5 miles or so at a time and it is all stop and go traffic so the amount I would have saved in gas was not that much. After installing the machincal fan the overheating issue stopped but now I am getting both O2 sensor codes it is something like 0149 and 0156 <-- probably not correct pulling this off the top of my head, I will get the correct codes and post them. The codes started happening prior to the overheating but one of the jeep guys that works in my dealership said it was most likely because the fan relay sends information back to the computer. Is this not the case? If not then I have a bigger issue.
Please let me know and I will get the correct codes for the O2's posted later today.
Thank you,
MM

The actual codes are P1491 engine radiator fan relay circuit and P0135 02 Heater Circuit ( Bank 1, Sensor 1)

I would like to get P1491 corrected before I start trouble shooting P0135.
Please let me know what you think.