'95 Cerokee won't start!!!

I replaced the crank sensor about 1.5 years ago because I had the same problem. I recently took it to a quicklube place and had the oil changed as well as the air filter. The very next day the check engine light came on and the electric fan started to run after the engine was turned off. The time interval got longer and longer and now it will run for hours. I eventually unplugged it. Now yesterday it had a tough time starting. A very rough idle then it would even out. Today, nothing. I tries to start, but no go. I noticed white smoke. I took it to auto zone few days ago and the error codes said the harness to the O2 sensor was possibly bad.

Any ideas???

Thank you...

I replaced the crank sensor about 1.5 years ago because I had the same problem. I recently took it to a quicklube place and had the oil changed as well as the air filter. The very next day the check engine light came on and the electric fan started to run after the engine was turned off. The time interval got longer and longer and now it will run for hours. I eventually unplugged it. Now yesterday it had a tough time starting. A very rough idle then it would even out. Today, nothing. I tries to start, but no go. I noticed white smoke. I took it to auto zone few days ago and the error codes said the harness to the O2 sensor was possibly bad.

Any ideas???

Thank you...

What code is that? You can measure voltage from a hot O2 sensor with a DVOM (digital volt ohm meter), about 2.5 volts. The harness can be check visually.

I don't think the fan has anything to do with the O2 sensor though.
Sounds like an overheat situation...does the white smoke smell like burning coolant? Pull the spark plugs and look for evidence of water or coolant..then we can talk.