Today while I was out driving in the country, my 2001 Prius with 140,900 miles pulled an error code. The red triangle popped up on the dash along with a "Check Engine" light and the car symbol with the "!" through it came on the MFD. I was able to get it back home safely by the way. The car had a weak 12v battery as it is, and I have been planning on replacing it but haven't gotten around to it yet. What I want to know though is, can a weak 12v battery cause those warning lights?
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.
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.
What is the proper battery for replacement? The one we had in there was a Panasonic, rather large and heavy. Now I ordered a replacement, it was much smaller, didn't quite fit in the bracket of the trunk, AND the terminals are too small for the clamps.
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).
Okay, no need to reply on this post. I flipped the car today and its all gone now. I'll post pics later.
