Moonlite is on the money.
99% of the time it is in the curly-Q pigtail at the upper controls that cause the 02 fault code.
02 is an interruption in communication between upper and lower controls.
One or both of two wires of the five wires in the cable are at life's end and causing this interruption.
There are two 12v positive wires (red and black) one Ground wire (white) and two Data Link wires (usually blue and orange).
It will be the Blue or Orange wire that is causing the issue.
If the issue is only intermittent connection of wire strands in the harness no damage should happen to the ECM or Platform Circuit Board.
However, if a short should develop between a 12v+ or the Ground wire and one of the Data Link wires, permanent damage could result to the ECM, The Platform Circuit Board or both.
Disconnect the pigtail at both ends and do a continuity test between both ends. Clip the ohmmeter leads to both ends of each wire and stretch and relax the pigtail while noting the ohmmeter reading.
Also be sure to check for crosstalk between the wires as well.
