Here is the mystery on my 05 XC90 where the AM/FM radio was cutting out and now is totally dead. You push radio on button,...

My key turned out to be the issue when immobilizer issue prevented starting the engine. Can you set alarm successfully? As in, when locked, does your red dash light blink, if you leave window open, then open door to see if alarm goes off. It is a matter of process of elimination before replacing parts unnecessarily. Does you engine crank or not? Just too many issues without knowing more.

For others who have same issue as this, as I did, first place to check when a vehicle just dies is the fuel pump. They tend to get weaker and weaker, then will simply not pump enough pressure to allow engine to run. If you check the fuel pressure valve located on the end of your fuel rail, called a Schrader valve, it is like a tire valve, so depressing the valve should squirt some gas out, so have a rag over it, and if no gas pressure, then likely it is fuel pump. Of course, sometimes it is fuel relay or fuse, so those are simple enough to check first.

If your engine is smoking out the exhaust, and sucking oil into engine, which I had happen, it is usually a sign that the two CCV hoses which cross over the back of your engine over the intake tubes if engine cover is off on the 4.4 motor X5’s, squeeze hoses, if they are spongy, this is indicator they are restricted and when this happens they suck oil into engine cylinder, as crazy as that sounds, it happened to me. Left side exhaust only. I replace all components and hoses, never had an issue since with over 100K miles driven.

It is likely your heat control valve located in your engine bay, look for the hoses that enter your fire wall, then follow them and you will see the control valve, simple to replace.

The warning for air suspension inactive is only able to be cleared by dealer or shop that has BMW diagnostics program. I have had my notice on for years, just ignore it, you always know when one of your air bags leak down, it is obvious, so who needs warning message.

For those who are changing alternator, it is not necessary to remove radiator as most DIY videos will instruct. It is a tight fit, but simply put cardboard protection against your radiator and you can wedge alternator up and out with no damage. It is a tight squeeze, but you can pull it out an put new one in without the extra wasted time pulling radiator out. I always look for short cuts on my vehicles when it comes to repairs.