So with my cars being 7 & 8 years old, is the TCU battery a maintenance item that should be replaced at this interval or sooner? Or do you just wait until it fails ? I know its rechargeable but I got to think it doesn't last forever. I Haven't seen or read about anything about this battery. I question this as my Navigation system is telling me I'm 50 miles away from home and continues to change even as I drive. Dealer is telling me it could ne the Battery, Antenna, TCU unit, etc. Rather than play this guessing game, I've decide to upgrade to CarPlay and just forget about it, except for the battery.

 

I just replaced my TCU battery - easy to do. Turned out the old one was probably still okay, but at least I don't have to worry about it for another 6 or 7 years!

 

The battery pack design has changed at least once over the years, but for my car it was a two-cell pack. One cell is rechargeable, the other not. There are several threads on it. Search for "SOS System Limited Functionality". That's the telltale warning message, although there is at least one other cause for that particular warning.

 

If you need it:


I've seen it for less on eBay, but not at the moment.