Code P0138 in 01 GP GT

[TAvsGN]

Been having an intermitent SES light come on in my wife's 01 GP GT. Had it scanned today and it showed P0138 is history. Guess this is O2 sensor, high volt bank 1 sensor 2. This is referring to the post-cat sensor correct? Light has come on twice in the last 3-4 weeks. First time was after about a 2hr drive. Second was when she was stuck in the snow. Light went off after a day or two. About 4 years ago, I had to put a new cat convertor on it. Put on a high flow unit and it starting kicking an SES light then. Can't remember code but think it was for something like too much flow for the computer. Put an O2 simulator aft of the cat and haven't had a problem since. Then a couple months ago, I got a light for the EGR valve and replaced that. No more lights for that. I guess I am looking for any advice on what could give the intermitent SES for the O2 sensor. Car seems to run fine even though I rarely drive it. Could the O2 sim be bad now? Thanks for any help.

[BNaylor]

The DTC relates to the post CAT 02 sensor only and should not affect driveability. The PCM module has determined that the 02 sensor (simulator) or something in the circuit is shorted to high. So you either have a bad simulator, electrical connector, or wiring back to the PCM module. Also, maybe there is moisture in the electrical connector.