Pretty near all of these suggestions should throw codes.
I’d start with a “2nd opinion” from another OBDll reader.

Basic engine/emission related codes are generic.
For now, most auto parts stores will happily come
out and scan your vehicle right in their lot.

Speeds 1,2,3 & 4 indicate that you have MCC (Manual Climate Control).
I agree with Neil - Sounds like your fan speed control has packed it in...

And get those engine codes checked out. Your Check Engine light probably has messages stacked up for you. The good news? If the service light just comes on for two minutes when you start the car, it’s only reminding you that you’ve exceeded your mileage triggered service interval. It can be reset an...

Sounds like the resistor to me, as to my knowledge that's the only thing controlling blower motor speed is the resistor. These are easy enough to fit and pretty reasonably priced. Here's a link to what is potentially the same problem by another poster on this forum: click me Not true. If the MCC fa...

IIRC-
Running, the doors will lock with the key in,
using the interior switches, but not the fob.

Engine stopped, door opened, then closed,
the car won’t let you lock the car at all if the
key is in the ignition.

IIRC...

Both of the antennas in the rear side glass use power amps. Since your new unit probably doesn’t support dual antenna diversity tuning like the Alpine/OEM unit, the big one will do. Just make sure that you connect the power antenna connection from the adapter harness to the mating output on the new ...

Yes - There's a fuel pump access plate, but - As the P80 was originally FWD only, and the AWDs have a dual pump system and a saddle tank to provide clearance for the rear drive shaft, the AWD pumps are in different spots. and it's pretty much useless. I haven't had the pleasure of dropping the rear ...

Is your Check Engine light on?
Have you scanned for codes?
Checked fuel and spark?

Finally got a minute to review the diagrams. There are only 4 wires to worry about here: Seat Power 12 VDC (+) is Green/Red protected by an auto reset thermal circuit breaker in position 11C/39 - Amps Unknown... ( Anybody have the cover off their fusebox that can have a look? ) Ground is the black w...