I'm reading threads about various problems that can't be solved with junk yard parts without a lot of work because the parts are programmed to a specific car. The rearview mirror and the heater controls were recently discussed.

Why? Is this to destroy the used part market?

Is this why I paid less for my car than I would have paid for used Taurus of similar vintage?

 

Actually that is some software protection.
F.e. We have 2 modules CEM & ECM.

CEM is always broadcasting messages with configuration info.
ECM listen for it. This configuration messages contains info what functions ECM should support what event to listen and so on. So when ECM received such message it checks if it can work together with CEM (that means all necessary functions supported and so on). If something goes wrong ECM goes to limphome mode and does not sends nor received any info to/from CAN network. It works in standalone mode. It this case and error code with number E00X is stored. (wrong configuration).
So this protection just ensures that 2 or more modules can work properly and communicate to each other in proper way.
Its a lot easier to make firmware for some predefined configuration that make some general program for a module that will work with all other modules that car can contain.

So that is just to make cheaper development of the car.

So disadvantage is that modules from different cars is often does not work with each other.

 

Meh. Why stick any sort of car specific circuitry into the mirror?

I'm going to go with "We found a profit center and boy can we stick it to the people that bought our cars."

My car only came with one key so I went to the dealer to get a second. I was told that it was $65 for the key, $25 for the "software" and $95 to install it. WTF? Nearly $200 for a key. That's a nice piece of change for the dealer.

 

Mirror contains electronic module. And remotes are programmed in it.
Programming this module needs to obtain pin codes from volvo.
Pin codes are tightly coupled with the car because of security.
So mirror from the junkyard means wrong pin code and even dealer cannot program new key to it.

 

Why? Why not put that circuitry on a board in the dash?

 

Just ask Volvo engineers .

Now we have what we have.

New models of s80 2007- MY, v70/XC70 2008- MY
Do not have such design.

 

When I win the Powerball, I'll buy a new Volvo. Until then, I'll continue to complain about the cost of keys and rearview mirrors.