Coolant Temperature Gauge Fluctuations?

Just to close the loop here. I figured out what was wrong. 2 things:
1. The upstream air/fuel sensor was shot. I noticed that when it was acting up, the 02 reading would peg out at like 5.1 volts every time the car went into closed loop. This made the STFT 25% in closed loop and the longer this want on, the higher the LTFT became. I changed the air/fuel sensor and the fuel trim issue went away.
2. While the car was running I wiggled the coolant temp sensor harness and saw the temp drop to -40 degrees on my scanner. When that happened, P0183 was also tripped immediately. Not sure why, but I think the very cold coolant temp made the PCM “think” the fuel temperature sensor was acting up as its temperature did not have a corresponding drop in temp. I further analyzed if the wiring of the coolant temp connector was bad or if the connector was not seated well. It turns out it was the connector as no matter how hard I pushed it, it wouldn’t click into place. Swapped the connector with a pigtail and it snapped right into place. Problem solved.