Outside temp sensor

Ran over a curb lately? The sensor is bad. It's usually in the plastic under the front of the right fender. It may have gone missing entirely if you got up on a curb..

Fix is a new one. Cost is about $40 for the part. Figure 1 hour labor for a dealer to install, 15 minutes for an independent, 5 minutes for a competent DIYer.

The sensor is located in the left side air ducting that directs air onto the front brake assembly.

The sensor should be more reliable than what you expereinced, my guess is that it has come unplugged or the wires are otherwise damaged.

Iscraped the sensor on my E39 & got the same readings. When I soldered the wires, my readings became a bit whacky. Seems to be off by 5-10 degrees, at least &not consistant. My guess is a change in capacitance from the solder job. As such, I suggest replacing the unit & wires instead of trying what I did.