458 Broken Mirror Consequences

I recently pulled the bone-headed move of clipping my drivers side rear view mirror on the garage wall while backing out. I typically pull the mirrors in when I get close to the door, but this time I had a brain fart and neglected to do so. The mirror hit the wall breaking the glass and the plastic housing. After the cursing was completed, I pulled the car back into the garage noticing several red lights on the dashboard. The check engine light was on, the TPMS light was on and the ambient air temperature display was dashes.

As it turns out, the outside ambient air temperature sensor is in the mirror. It is a small, finger-like projection underneath the mirror. While this supplies the information to the air temperature display on the dashboard, it also serves various other functions.

The engine ECU uses this sensor as a rationality check for the intake air temperature sensor for the engine. If the two do not match within some tolerance the computer throws up its metaphorical hands, says there is an error and illuminates the check engine light.

The HVAC system evidently also uses this sensor for the A/C. While my sensor was broken the A/C would not blow cold air. The correct operation returned when the sensor/mirror assembly was replaced.

But wait, there's more! The TPMS system must use this senor to compensate for air temperature effects on tire pressure. (PV = nRT) Again, when the sensor was missing the TPMS light was on. When the sensor was restored, the light could be reset.

Finally, the VDA will not work if the sensor is bad.

This is a large load for a $0.25 thermistor (for which Ferrari charges several hundred dollars). The mirror glass and (plastic) mirror housing are also ridiculously overpriced.

 

I know the replacement cost. The mirror housing with motor and temperature sensor (the only way it is sold) was about $1900. The glass was about $800. It then has to be painted, another $1000. Because it was the memory mirror and electrochromic (auto dimming) it was more expensive. The non-electrochromic mirror glass is "only" $100.