Auxillary Battery

[Kaya]

My central locking on my Toyota Prius is not working. I changed the Battery on the FOB with no joy. I have checked the auxillary Battery in the boot and I am getting a reading of 12 V. Should I still look at replacing the auxillary Battery or is there another issue I need to investigate

Any suggestions will be most appreciated

[TonyHSD]

12v is low. Needs to be 12.3v and above, ideally 12.5v when you unlock and measure the car. If your Battery is older than 5 year’s perhaps it’s time for replacement. Toyota dealers has the best price for these and the right choice. Don’t just buy any Battery, make sure it’s oem specs. 
 

[Joseph D]

11 hours ago, Kaya said:

My central locking on my Toyota Prius is not working. I changed the battery on the FOB with no joy. I have checked the auxiliary battery in the boot and I am getting a reading of 12 V. Should I still look at replacing the auxiliary battery or is there another issue I need to investigate

Any suggestions will be most appreciated

Your 12 V Battery is not likely the issue with your central locking, although it could do with a full charge-up using a good fully automatic Battery charger with an AGM setting.

Does the little LED light up when you press any of the buttons on the fob?

Did you install the Battery with the +(positive) side up?  The + side is marked on the battery.

Do not touch both the top and bottom of the battery (e. g., between your thumb and forefinger) together with your bare fingers, as it will dramatically shorten (pun intended) its lifespan.  Use gloves or an insulated pair of tweezers to handle a button cell battery.

Out of interest, you should measure the voltage on all new button batteries (for any application) and ensure it measures above 3.2 V or more.  If it is 2.8-2.9 V it is pretty much dead.  I have had more than a few dead button cells straight out of the packet.

YMMV.