I have a 2001 V70 2.4t, auto with 165k. Last month I noticed it would crank kind of slow and figured it was due for a battery. I didn't drive if for a few days and when I tried to start it the battery was dead. I took the battery out and took it to local auto parts store thinking I would just buy a new one. They tested the batter and they said it was fine, and to put it back in a bring it back for a systems test. They tested starter, battery, and alternator and concluded everything was fine. I drive the car for 2 weeks, no issues, no slow cranking, and yesterday I get in and it won't start. Cranked slow and then just clicked. I put the battery on a charger and (don't disconnect negative terminal), get a full charge, try to start and again cranks slow, then starts and I get dash tag IMMOBILIZER SEE MANUAL. I let the car sit how it is for 10 hours, get in the car and it fires right up. I'm confused as hell, and I'm not sure if it's the immobilizer or a parasitic current draw?? Or could it be an immobilizer causing a parasitic draw??

 

I think the CEM module hung somehow because of low voltage.
Or it started dying (Usually that causes a lot of other messages to show in the dash)
Next time try to reset with disconnecting the battery.
Before disconnecting you should wait for about 5 minutes with ign off.
Connect the battery with ignition in the II position.

 

Last night I disconnected battery, gave it a full charge, reconnected everything and it fires right up, I turn it off for 10 seconds fire it right back up, turn it off again and the third time cranks slow, starts and get IMMOBILIZER message again. I get the charger back out and it says the battery is dead. I went back to the store that originally tested it as a good battery, and bought a new one. I'm thinking that maybe the battery had a dead cell the whole time, but still tested as good, as there is no possible way a battery could be dead only connected for 2 mins, and 3 cranks. So far so good.