i just got my 95 grand cherokee 2 months ago and replaced my o2 sensor last week and my check engine light comes on after 5 - 10 min
i read the chiltons manual and it says that if i replace the o2 sensor that the pcm might throw a code because theecu thinks there is a problem now that a new signal (clean o2 s.) is coming in. schucks will scan and reset the o2 section on the pcm for free, we looked for 5 min and the scan port could not be found.
o.k. the question is : where is the scan port ( chiltons says the port is under the driver dash, and has a pic of what it looks like, and my under dash looks nothing like that )
i'm sure this is easy for any long term zj owner , but i'm new and still learning
thanks for any help , chris

yup this is easy. You don't have the scan port, that is only on vehicle with OBD II (96 and later). To reset your CHECK ENGINE light disconnect the negative battery cable and leave disconnected for 5 minutes.

Have you checked you codes to make sure it's the code for the O2 Sensor?

Turn the key to the ON position, then OFF, then ON, then OFF, then ON - leave it on this time, the CHECK ENGINE light will begin to flash the codes, the codes will be in double digit form with a short pause between digits and a long pause between each code.

example:
flash pause flash flash - 1 pause 2 = 12
pause pause pause pause
flash flash flash flash flash pause flash flash flash flash flash - 5 pause 5 = 55

code 12 - battery was disconnected within the last 50 ignition cycles.

code 55 - End of fault codes.

Just post your code(s) and we will let you knwo what the code(s) means.