Temperature reading problems

You could have a problem wire in the wiring bundle to the passenger door that is intermittent.
When the weather cooperates I would remove the door panel and grab various groups of wires and move them around while watching the display screen for the HVAC and see if you can narrow it down.
The common area's for chafed or broken wires in the door harness is where the window goes up and down and might be in contact with some wires. And, also where the complete harness goes through the boot between the door and chassis (A Pillar area).
This harness is being flexed every time the door is opened and closed.
And lastly if you haven't found it by moving wiring around then I would disconnect the connectors to all things in the door that are related to the HVAC and inspect the electrical pins and sockets closely for any damage, bent pins, corroded pins and sockets, etc.

BMD wrote:

Could it be a sensor?

It could be a lot of things including a sensor. But given the fact that the problem didn't surface until you pulled the passenger door panel, I would continue to look in that area for the problem. If after checking everything possible in the door, then you can check dashboard sensors. Would have to look in the FSM for specifics on those. It would be hugely coincidental if you had a sensor go bad at the same time as removing the door panel.

Thank you very much for your information Rick. Since I was going to pull the door panel today, I went ahead and did it anyway because I too would like to know exactly what the problem was. I moved the groupings of wires around but I wasn't able to reproduce the flashing in the HVAC display. I looked for chaffing and inspected connectors, but didn't see any damage or corrosion. I sprayed the connections with electrical spray just in case. If this is intermittent I will have to re-visit the cause if and when the flashing re-occurs.