Could the 12v battery be causing this?

Maybe.

 

The computers that drive our car are all dependent upon quality 12 V. supply and once the car is started and running, the power comes from the inverter. However, power problems can cause all sorts of 'strange stuff' and misleading symptoms.

One of the best things to do is to read the 12 V. battery voltage when the car is running or in "Ready." If it is 13.9, you're OK . . . now. But there can be transients when starting and a weak battery can lead to sags and all sorts of random stuff.

Bob Wilson

 

Charging current is supplied by the DC-DC converter, not the inverter.

When a weak 12V battery is suspected, battery voltage must be measured with the vehicle OFF (not READY). With the vehicle running, one is measuring charging voltage from the DC-DC converter, not battery voltage.

 

When and how was this determined?

Yes.

 

Then replacing it should be the first step.

I had asked for additional information because I wanted to more confident that your 12V battery needed replacement, before suggesting that step. Thanks for responding.

 

It sounds as if the original battery had been replaced with a kit that used a different size battery and put SAE clamps on the terminals. You've bought a replacement, OEM battery with terminals sized for the original clamps. What to do is going to be a challenge.

Can you exchange the battery?

It may also be possible to order the original sized clamps from Toyota. Alternatively, get them from a salvage.

Bob Wilson

 

The proper battery would be another Panasonic, if you can order that from your Toyota dealer.

If that battery is no longer available, then you could improvise by finding another battery that will fit into the space.

If you want to go back to the original GS battery, then you'll have to replace the terminal connectors and the battery bracket (since a larger bracket was required for the Panasonic battery).