Does leaving the fob in car do anything.

having the fob within range of the car puts more drain on the fob battery and 12v as the fob and car communicate.
other than that, i can't think of another issue.
you will need a more prius aware scanner for the correct code and sub code

 

Fob Battery goes bad quicker...

 

It's the way these new smart keys work.

The fob needs to be in radio communication with the car to serve as a control device.

Normally the car polls for the key every few seconds. This poll-and-sleep recheck behavior is done to save battery power.

Once the car detects the key nearby, it changes to continuous polling so that it can respond instantly if needed. Because the radio usage is constant, this mode uses more power.

This works fine for owners who remove the fobs from the car when they are done driving.

You may need to plan on additional 12v charging.

 

I’d start taking the fob with you, prep for possible replacement of current battery, and depending on what you currently have, maybe invest in a newer, smart charger, in 4~5 amp range.

 

The cold didn't do your batteries any favors either. Put the 10A charger on it for a couple of hours. Then go back to the Irish auto parts store; have them run a battery check/load test. If it's good, keep an automatic trickle charger on her, otherwise replace the battery.

Hope this helps...

PS. also check the electrolyte levels before charging - I'm pretty sure you have access the battery using a quarter to unscrew the plugs.

 

I assume you got the "low FOB battery" warning, not the "low 12V battery" warning.

By the way, you are posting in the Prius Prime (PHEV) forum, but your signature says you have a 2019 Prius Limited, the normal Hybrid, not the Plug-In.

This would be due to the car not recognizing the fob due to low fob battery.

When you say car started and then shutoff, are you saying the gas engine was running and then it shut off? Did you check to see if the Defroster was running?

So now you've drained the 12V battery because for some reason it wasn't being charged while you were warming it up. For some reason, your car must not have been in READY mode.

The Prius will charge the 12V battery when you are in READY mode and not in Neutral. It doesn't matter if the gas engine is running or not. It uses the Traction Battery to charge the 12V.

Doubtful the Check Engine Light is related to your battery issues. However, a code reader needs good power and the car to be in READY mode in order to scan the codes. Maybe the Irish auto guy didn't have the car in READY when trying to read codes. You will still get power to the code reader when you plug it in to the car because the OBD port is always powered. But it must be in READY to read any codes.

 

I always use the Battery-Saving function on my fobs when not in use...
PriusChat won't let me upload a screenshot right now, but Page 178 of my 2017 Owner's Manual explains how to disable the fob battery.

 

Here you go:

The other way is to place your FOB in a Faraday bag. I highly recommend this - you do need to close the bag to prevent signals from going up and out of the bag.

Hope this helps....

 

I found it on page 736 of my 217 Owner's Manual. It actually says that your fob can be turned off, but the dealer has to do it for you. I plan to be out of the country for a couple of months starting next month. Would it make sense for me to just remove the battery from the fob while I am gone?
Ray

 

I don't know why the Prime is different (having to get the dealer to disable it), but in your case, yes, I would remove the fob battery. For long-term storage, look up T-SB-0037-20, Long-Term Vehicle Storage Guidelines (since file uploads aren't working yet.)

 

I would get a second OBD II scanner and try again. It sounds as if the car drives just fine after a jump start.

 

I thought any electrolyte checking and topping off was suppose to be done with a fully charged battery.

 

ideally, but if you let the electrolyte level get below the plates - I was told that portion of the plate is irrecoverable, even after topping-off. Don't know if that's true or not; because I never let my lead-acid batteries get that low.

 

I know the electrolyte density, thus the level, changes with charge state. Top it off before charging, and it can over flow when charged. That results in the electrolyte concentration being off in addition.