Red triangle came and went

You need a mini-vci cable, and Techstream will read this stored codes properly.

 

i suppose it could be the first sign of a bad battery, hopefully a code is stored. swing by auto zone and see what their reader shows. also, have them test the 12v. if no luck you'll need the mini vci as sfo recommends above, to a dealer. all the best!

 

I don't think a wheel speed sensor would ever light up the RTD. That's usually a "fatal" problem with the hybrid system, or as bisco noted, a bad 12 V battery can cause all sorts of errors. Check the "resting" voltage, which should be about 12.4 V.

Have you noted any signs of hybrid battery problems--fluctuating charge level, cooling fan (rear seat grille) noise?

Another simple test is checking for flow in the inverter reservoir--push power button twice, foot off brake, open reservoir and look in with a flashlight, and listen for an aquarium pump hum.

 

Since you are still interested in what caused the red triangle, go to any autoparts chain that offers the use of a scanner for free (as Bisco said above) or go to the dealer and have the vehicle checked/scanned.. either way be sure to have all the codes written down for sharing.

 

How are you measuring that 12.1 volts, with a digital voltmeter, with the car off? That's pretty low.

 

What I was thinking... Was there a load on the battery when you checked? In accessory mode maybe?

 

The noise after you turn the car off is the engine coolant heat recovery system, not the inverter pump. Some squeal a little louder than others, which could be cavitation. That might be solved with bleeding the system, but it's not applicable to your current problem at all.

The copy of Techstream sounds like it's pirated, but you don't get a subscription which is probably the real value. There are no manuals, very little in the way of menus, obviously no support or updates. It's not very robust, either, running off an old laptop, but when you can figure it out and get it to work, it sure is a nice tool.

I agree, get a voltage reading with some load on the 12V battery in ACC mode.

 

My bought new 07 launched a RTD on me today. First cel ever seen on my car. I thought oh no it's the hybrid battery but the RTD only came on for second. That's the sign of a dead 12 volt battery but my well cared for monthly maintenance charges optima is only 3 years old.
Hooked up techstream and got a
C2318
Low volt power supply

That's the 12 alright. Next page diagnostics in ignition reports 7.3 volts on the aux battery. Lol. So looks like my not that old optima took a dump on me.
On the charger now. Probably has a bad cell. Disappointed.

Will let it sit on charger overnight and load test it in the am. But not looking good,

So yeah s#it happens.

 

A cheap multimeter will also suffice. Good for lots of other stuff too.

 

What happens to the voltage when you push the start button another time while in that test mode? That will add fan, headlights, power windows, etc.

And you're right about free scans. They don't read the hundreds of Prius-specific codes, not to mention INF codes. And one time they even gave me the wrong number off the scanner. Definitely worth every cent I paid for it.

 

Wheel speed sensor issue will not trigger red triangle warning light.