This is the first real issue I have on my 2005 S60 2.5T AWD.

Today I got the "immobilizer, see manual" message for the first time, and couldn't start the engine. After checking the battery voltage with a tester you plug in the cigarette plug, out of the blue, the engine started. I proceeded to get home when I noticed that instead of the usual "D" displayed on the dashboard for the gear selected, I had a "-", and to me it sounded the engine was in 3rd gear.

Things got weirder when I was stopped at a traffic light, as the "D" re-appeared, and when the light turned green and I pressed the accelerator, I felt a distinct clunk on the gear "engaging", that I never experienced before, and the "transmission service required" error message came up. At that point the "-" came back up replacing the "D". That sequence happened another 2 times until I made it home.

I finally got home, parked and tested the battery with the car running, and it indicated both the alternator and battery being healthy. I stopped the engine, and tried to start it again. It didn't start. I still had the "transmission service required" error displayed.

I left the car for about an hour, and came back with a voltmeter, and measured the battery at 12.60V under no charge, which seems to be healthy. Then I tried to start the engine, and it did start. But I got an extra error message, "engine system service required".

I got the S60 in 2013 with 103K miles on, and things have been great with regular services every 7.5K miles, and the need to get new support arms and right half-CV axle. Worth to mention, I got a "deep" service at 105K miles, on top of the dealer's, including a transmission fluid flush, by an ex-Volvo mechanic. The car is now scheduled for the 172.5K miles service, at which point I was going to get the transmission fluid flushed...

All those different error messaged made me think the battery was under-powering the car's electrics and electronics, but it doesn't seem to be the case. Any idea, anyone?

 

I would get the batter fully tested. Voltage alone doesn't always tell the whole story and you may be onto something with the thought it isn't sufficiently powering the car. I have seen some pretty weird things happen when a battery develops an internal problem.

 

Thanks for the advice! Long story short, inspecting the battery, and looking for a possible replacement, I realized that it was made in February 2012, and had a 3-year warranty. So a replacement was due, and that's what I'm doing tomorrow, we'll see if that alleviates my issue.

 

So, I replaced the battery, installed the new one, and voila! All issues solved. Now I just need to get an OBD2 reader/scanner to reset the Check Engine light.

 

Good to here it was that simple. Like I said, I seen some pretty weird things happen with a defective battery. Thanks for reporting back confirming the issue. It helps others here with a similar problem.