Gear lights flashing MFD stays on when car is off

Welcome. You might spend the rest of your life switching out parts and not find the right one or ones. There are probably other codes that your reader isn't seeing unless it's able to talk to all the computers in a Prius.

A quick Google search turned up this thread which looks like it might be helpful. U0293 Lost Comm w/ Hybrid Powertrain Control Module | PriusChat

 

check the negative to ground connection and the voltage at the front jump point

 

It sounds like the DC/DC converter is working. No surprise; they rarely fail. You do not have an alternator.

I think I would suspect mice as the culprit before water damage, but either requires lots of visual inspection.

 

check the voltage at the jump point under the hood withthe car off, to make sure you're getting from the battery to the fuse box.
if the fuses have continuity, jerry might be right about a damaged wiring harness. could be rodents or just corroded connectors.
or it could be a bad ecu.

 

The problem is definitely intermittent and we've not yet been able to figure out exactly what is resetting it when it works again.
Today, we checked the HV traction battery as we weren't hearing the relays engaging. Upon metering the low voltage side of the relays, I was getting 9.6v, in spite of reading 12.6v at both the battery and the jump terminals. With the Red Triangle ️ of Death and no Ready light, I hooked up the battery charger...just because.
At that point we began putting the HV battery covers back in place, I reconnected the auxiliary battery and pushed the power button. The system came on and went into Ready mode, along with the red triangle ️ of death and the vehicle icon on the MFD was red with an exclamation point; it is my understanding that this indicates a problem with the HV traction battery. In addition, the dash lights (speedo, gear indicator, etc) were not on in spite of the fact that the car was running and I could drive it. At this point I shut it off and disconnected the positive terminal. Upon reinstalling the positive terminal and pushing the power button, the car came on and the dash lights functioned normally; the red triangle ️ of death and the was on along with the red vehicle icon at the top left of the MFD. A few minutes later, the triangle went away, and the vehicle icon turned green. At this moment, the car is working. I checked the voltage at the HV traction battery relays and the contactor side is at 13.8v on the coil side of the contactor.

This intermittent issue has us stumped, and the fact that the car won't drive when it's malfunctioning makes this much more than annoying.

 

you might need a new combo meter. lots of threads here:
is-this-normal-combo-meter.229391

 

the red triangle and exclamation just means there's a problem. you have to check the codes to find it.

13.8 means your inverter is working, but doen't mean your battery is good.

 

did you check all the modules and connectors for corrosion with the battery open?

 

I did not see any corrosion on the connectors, but there was some bluish fluid on one of the modules. I ran the DrPrius app tests and it said the battery is still doing its job.

The auxiliary battery is brand new and swapping the batteries between the two Prius' yields the same results; the one Prius is perfectly fine, this one has the same intermittent issue.

 

bluish fluid is corrosion, usually leaking electrlyte, which will cause the triangle

 

of course

 

You switched the HV battery between the two vehicles, and still have the same issue?

Has the dealer performed a diagnostic obd2 scan on the vehicle, or are they angling for you to trade it in on something else?

You're not the only one.