P0150 may be because of a poor contact in the connector on your driver side pre-cat O2 sensor, which may have only intermittent contact, keeping the system from going into closed loop, as this DTC code indicates You already found poor contact was made better simply by unplugging and then plugging back in the O2 sensor harness connectors. If the O2 sensor harness connectors are in fact causing poor contact to the sensors, get that sorted out. If the harness connector does not look clean inside at the contacts, use a spray cleaner to get rid of the crud inside of it. If the female contact pins are a bit worn, they might not be making good contact with the male pins on the O2 sensor. If that is the case, you can fix it up by taking a needle-nose plier to the sensor pins, giving them an ever so slight twist of a couple degrees so that the slight interference fit the pins should have is improved to make the contact no longer intermittent. Good luck.