Ambient temperature sensor - invalid signal

[ZPM]

I have a 2015 X5 which is rarely driven, and mainly sits in a garage. I was very surprised to start it recently and find that the trouble light was lit and the A/C would not work. The instrument panel IP) was showing an outside temperature of -40F (impossible). Using ISTA+ I found the following codes:

B7F655 - Instrument panel: Outside temperature sensor Short circuit to B+
D0142C - Instrument panel interface (ambient temperature, 252.1.4): Signal invalid
D3542C - Signal (ambient temperature, 252.1.4) invalid, transmitter KOMBI
D4142C - Signal (ambient temperature, 252.1.4) invalid, transmitter KOMBI

I performed the test plan, which consisted of removing the sensor connector and shorting its two wires. If the IP then shows +122F, the sensor needs replacing. Seems the temperature sensor is a thermistor which takes a fixed voltage from the IP and returns a lower voltage based on temperature. The highest return voltage indicating the highest temperature.

In my case, the IP continued to show -40F when shorted. This would lead me to believe that one of the wires in the pair is broken between the IP and the sensor (maybe both). Though, B7F655 makes it sound like the return wire is somehow suddenly spliced to +power. This would jive with the "invalid" signal vs. "no" signal. I checked for any wire fraying or animal chewing and found nothing.

My next idea is to remove the IP and to short it at the connector there. Before I go to that effort I wanted to see if anyone had any experience or idea on this. It seems odd to me that this wire might spontaneously break just sitting in my garage for months (it wasn't broken the last time I drove it).

A note: earlier in 2021 I did have a spontaneous wire breakage in the control wire that runs from the ECU to the radiator fan. No damage to the harness or either connector. Just sudden lack of continuity one day. I ran a bypass to fix it. In 40 years of wrenching I'd never experienced a wire in a factory loom simply going broken until then. I accept that odd things can break in cars, but two wires breaking on their own seems a bit long on odds. I'm new to BMW's so maybe I'm missing something about them here. Is this more or less a normal problem?

Another note, the reason I started it up was to turn it around in the garage so I could replace the starter battery. It still started strong (on a battery maintenance charger) but was nearing 7 years of age so I decided to change it. I don't think this would trigger my temp sensor problem, but thought it best to mention.

[ZPM]

Just to close this up. I pulled my instrument panel and verified that one of the pair of wires connecting it to the sensor had no connectivity. I soldered in a bypass and the problem was resolved.

This makes two wires which have spontaneously become broken inside the insulation jacket without any mechanical stress on them. I've asked around and been told by shops and manufactures that the wire all comes from China, is not annealed, smaller gauges are being used, looms aren't secured against vibration like they once were, thus wiring is a major problem in auto service today.

[rarlequin]

Hi, what exactly did you do on the cluster? Did you do new wires from the cluster connector to the engine bay?