Red triangle apparently appears for low 12v voltage during drive

welcome!

i suppose if the battery is defective in some way, it is possible. since you need a new battery, why not start there and see what happens? are you gonna ditch the car if it's not the 12v?

 

Here's a similar thread that's old but was recently brought back up. That owner chased the 12v route but eventually turned out to be a bad hybrid battery. You need to get the trouble codes read to have a much better grasp of your situation.

Weird, intermittent indicator lamps (VSC, Battery, Triangle of Doom, "(!)", and Hybrid System) P0A08 | PriusChat

 

To add a little fuel to the fire, I ran into something new over the weekend. Car (Gen 2 Prius) has a previously rebuild HV battery, about 2 years old. Symptoms were the red triangle popping up while driving. Owner was resetting by disconnecting battery. Check the codes and the only code present was Block 2 becomes weak. Yet, freeze frame data shows only a 0.3 volt difference from high to low on all modules. Block voltages all looked decent after sitting all night, with about 0.2 volt from high to low. Reset codes and I sat in passenger seat with laptop while going on a test drive. Went through the same thing 2 more times over the next hour. Block 2 every time, but couldn't catch it. Came off the mini-vci and shifted to using android app with battery health check. Did some "hammer down" acceleration testing to get max current draw and max voltage drops. The app showed we actually pulled 150+ amps a few times on acceleration and 90+ on regen. No obvious problems, then driving a steady 65mph on highway, and BANG, triangle pops up. The only thing that made sense to me was a wiring issue.

We pulled HV battery out, stuck it on the bench and started inspecting. Everything looked decent, even the bus-bars looked good with very minimal corrosion. Then we throw a torque wrench on the terminal nuts. Holy crap..........got anywhere from 1/2 to a full turn on every nut in order to get to 48 inlb torque. SO, we pull the bus-bars off. The back of the bars, only on the negative side, were solid black, like BLACK. Even in the area that was sandwiched between the nut and terminal (which is normally perfectly clean copper). All the threaded terminals and nuts looked fine. Pulled the bus-bars out of the plastic strips and did a quick 15 second muriatic acid dip and swish. They came out looking like new again. We decided to go ahead and take a couple days to cycle the modules and plan to install the pack Thursday evening, with no other changes. So far, all the modules are testing pretty well balanced. Will be interesting to see if the problem goes away.

 

How was this verified?

 

That should work but it's always been my experience if there is a trouble light there is a trouble code. I use techstream.

 

The Toyota diagnostic software contacts ALL of the ECUs, other OBD2 readers only read a subset. I have a MiniVCI that uses an unregistered version of the Toyota SW. You may want to get on eBay and order one.

JeffD

 

The only lights we received were the red triangle, the brake warning and check engine light. And of course the red car with the exclamation point inside in the upper left corner of the MFD.

 

The red exclamation point is what throws when the 12 volt battery is bad. That's the only fault light you will see that doesn't log a code and it throws when the battery dips below 11.2 I think. Trying to remember when I saw my triangle what the voltage was. Its a courtesy indicator that your 12 volt battery is bad. That indicator does not log a code.

The red triangle is a master caution light. It will definitely log a code. if your not seeing that code its because your OBDII tester is not hybrid capable. Usually the hybrid battery is bad but will also have a little picture of a car in the upper left of the mfd. The turtle. I say usually becasue we are seeing bad hybrid packs non stop. Its the age of the G2 platform.

 

Sorry....I meant to say trying to remember when I saw the EXCLAMATION POINT what the voltage was.

 

You've rightly noticed that PriusChat is chock full of threads where anybody's warning lights, before any progress has been made diagnosing them, will be answered by three or four people suggesting to focus on the 12 volt battery rather than whatever issue the car's computers are actually reporting. You've also rightly (in my opinion ) questioned that a little.

As some other posters have pointed out already, you don't get the warning lights without trouble codes, but you sometimes get trouble codes that not every scantool can read (hence the common "I have warning lights but there aren't any codes" posts). I would recommend getting the codes read, and at least for a serious moment considering the possibility that they mean whatever the repair manual says they mean.

If you get a set of codes that really, honestly, can't be explained after making a diligent effort to understand what the manual says about them, then maybe comes the time to take refuge in "well, I think maybe a battery problem has made all these ECUs crazy". But you won't find me among those who start with that assumption before any serious effort to understand the codes.

Also, if you get a capable scanner and read the codes and there turn out to be a bunch of them from several different ECUs, that also should not be taken as some kind of sign that the car is crazy. The ECUs talk to each other, and many of them have defined trouble codes that they set only because they have been told of problems by another ECU. When you look up the codes you've read, you'll see which ones those are, and then the large set of codes will not seem so inexplicable.

In my experience, the most likely result of reading codes from a Prius, looking them up, and honestly working to make sense of them, is finding that the car is telling you exactly what it says it is.

-Chap