2005 Prius not charging 12v while driving. 195k miles

What you've written suggests that somehow you've convinced yourself that your ABS, traction and stability control warning lights are telling you about a problem with your 12 volt battery, despite the facts that (a) you've done a pretty good job of ruling out the battery as a problem area, (b) your UltraGauge is showing the voltage while driving to be perfectly adequate to charge the battery, (c) you didn't include any voltage readings of the battery (while the car is off) to show whether or not its voltage really is declining from trip to trip, (d) your ABS, traction and stability control warning lights are primarily there to warn you about problems with your ABS, traction and stability control, and (e) when cleared, they are likely to eventually come back if the problems they are warning you about have not been fixed.

What were you using to read for codes, when you found "no codes or pending codes"?

-Chap

 

agreed, you may have a parasitic drain, or something else. what is the stone cold battery voltage before and after charging? what battery did you buy, and what was the voltage when you installed it?

 

The gold standard would be to read the codes with a Mini VCI, but if you don't have access to one, it might reveal a lot if you at least collect and post the blink codes the next time those warning lights are on. There are a lot of threads (one I saw just in the last day or so) with details on where to jumper to trigger the blink code output, with pictures even.

Cheers,
-Chap

 

Just my two cents worth, the OP just mentioned "Yellow Top"

Could this be another story of a bad battery coming out of Mexico. It seems we see this a lot on this board.

Everything I see either points to a bad battery or a short, but .0014 drain is NOT a short. So, what else could it be?

Ron (dorunron)

 

Is that after sitting overnight? Or what? Also, how are you checking the voltage? Digital Meter? Software? What and where. At the posts? Jump Post?

 

Check the ground cable of the 12V cable connections. Including the ground cable connection to the body. Also check the 12V battery voltage with multimeter when Prius is at ready.

 

Sounds like its charging and maintaining a charge to me.

 

Would it be possible to read it after the Prius has set overnight?

 

idk, you can try acton toyota in littleton, they have a good rep. i have never had to make a repair.

 

Keep your digital multimeter in the car. When the warning lights come back on again, leave the Prius READY and measure voltage across the 12V battery and also at the dedicated jumpstart terminal in the main relay/fuse box next to the inverter,

If you find the voltage is still ~13.8V at that time, then the next step is for you to get Mini VCI so you can retrieve the DTC logged by the skid control ECU. Then you'll need to carry your laptop and Mini VCI in the car so that the following time the warning lights appear, you can immediately plug in to retrieve the fault codes.

 

Everything sounds normal to me. Overnight measurement and measurements when running. Not sure what is going on. Sorry, can't seem to help on this one.

 

Well, at some point, after spending enough time running down the whole "maybe my ABS, traction and stability lights are telling me nothing but my battery's bad", maybe it becomes reasonable to ask if they could be telling exactly what the engineers put them there to tell, and better-late-than-never read the ABS, traction and stability trouble codes so that it would be possible to start on fixing the car.

But maybe I'm jumping the gun and there are still more battery tests people want to recommend.

-Chap