Jeep O2 sensor problems

I have a 99 Cherokee sport, 4.0I6, 150,000mi. I had to replace the downstream O2 sensor wiring harnesses and sensor because they were ripped out by a stick.(Dont ask, its a jeep). I am still getting a code of PO138 that says high voltage to sensor. When I look in the Chiltons manual, its says short to voltage. What could be causing this and where should I start looking? The jeep runs fine other wise. Thanks for the help.
Jason