P3125 with info code 316

Hi I have an 03 prius with 250k miles it drives perfect, very strong in reverse, no stombles etc.

But afte about 30min of driving without warning the red triangle will come on, engine will shut off and I will instantly lose all power to move and have to coast to the side of the road (it can actually be quite dangerous).

I can turn off the ignition for 5 second, start and drive again, but once it is warmed up and had done it once it will keep happening every 5 min or so. If I let it cool down for an hour then I can drive again for another 30 min.

On a hot day it may only be 15min of drive time and on a very cold day I can drive for ober an hour with no issues.

I have tried bleeding the inverter coolant, and even tried running an engine floosh product through the inverter coolant system. I have also physically verified that the inverter coolant pump is spinning and pushing fluid through the system. (And I see SOME fluid movement in the reservoir but not a lot, sometimes it seems like it isn't moving, but I can hear the pump going and like I said I have verified the pump is moving fluid so I think it's just hrd tonsee sometimes?)

Codes are p3125 & p3100 and the INFO codes are 316, 392 & 159

The mechanic who pulled the codes for me looked it up in some resource he has access to and said that other mechanics have fixed the problem by replacing the MG2. I have actually had an MG2 go bad in a 2001 prius I had years ago and that car made a whinning noise and would violently shake etc (which was all fixed when I replaced the MG2 stator).
This car has none of that, and had a strong reverse so I don't feel like it is a shorted MG2 stator.

Here is some info I found on the INFO codes:

316 Generator Inverter Sinv. +B short in generator inverter stop signal circuit

159 HV ECU internal error. Motor ECU Communication Circuit Malfunction

392 HV ECU internal error. Motor CPU malfunction

One recommendation for the 316 INFO code is to check wiring/connections between the hvecu and inverter, but I don't think that would be effected by heat like my issue.

Next I plan to flush the transmission fluid, as I figure if the fluid is low the cooling would be compromised also I could have metal particles in the fluid possibly causing an intermittent short??

But as I said before, when it's cold out even with engine warmed up I can go full throttle up a long freeway hill climb and pass cars at 70mph with no problems so it really doesn't seem like a stator issue.

If anyone has any insight or experience with these sub codes I'd love to hear.
Thanks!

 

I also found this, though I don't fully understand what it is saying to be honest

"The HV ECU checks the line connection of the generator inverter stop signal circuit and enters the fail safe
mode (limited driving) if malfunction is detected.
DTC P3125 - Information code 316, 318
Wiring Diagram
Inspection Procedure
1. Check for open, short and +B short in wire harness between HV ECU GSIV and GIVG terminals and
converter & inverter assembly G-SINV AND G-GINV terminals. See HOW TO USE THE DIAGNOSTIC
CHART AND INSPECTION PROCEDURE .
NOTE: The generator inverter stop signal circuit has +B short
if the voltage between the HV ECU GSIV or GIVG terminal and
body ground is always more than 13 V with the ignition ON
("READY" light OFF).
NG: Repair or replace wire harness.
OK: Replace converter & inverter assembly. "

 

Anyone know what the GSIV and GIVG etc terminals are and where to find them?

 

ChapmanF:
Yes! The hvecu would warm up after driving a while and being on the floor there would be slightly exposed to outside temps. And heat always makes electronics less efficient. This makes a lot of sense!

Ok next step (when I get some time when I'm not watching the baby) is to pull the hvecu and and inspect it and the wireharness where it connects.

Can any 1st gen hvecu be swapped in there or does it need to be "married" to other ecu's etc?

 

Hey thanks, I may take you up on that! Just need to find time to have a look at mine first.

I have a friend that currently owns my old '01. He is rebuilding his battery right now so I could try temporarily swappingin his hvecu as a test maybe?

 

Well I bought a replacement hveco off ebay with the exact part number for $35 however the car won't goninto ready mode with it installed. Does anyone know if there is an additional step necessary to program thenunit tonthencar or something??
Or maybe I just bought a bad part?

 

Oooooh! Awesome, I'll go turn the key on, thanks!
Also I did confirm that the problem is with my hvecu getting hot. I removed the case and layed the board on the carpet at the floor of the passenger seat with the AC blowing on it keeping it cold to the touch and drove around all day without issues. (Other than me being cold in the car)

 

Ok it's officially fixed!
New (used) hvecu was the ticket.
Been 2 days now with lots of driving and no issues!

On a side note I did actually try to repair my original hvecu. There are 3 large transistors attached to an aluminum block heat sync that were getting very hot so I replaced all 3 with an NT equivalent (which work as replacements for the transistors but because they have a metal plate on the back which is connected to the middle leg it caused the case of the hvecu to have +5v running through it, so if it touched the frame of the car it would immediately shut down the car.)
Unfortunately though they did run cooler it did not fix the problem. There was another lone transistor that also got hot after a while and I suspect this is the culprit, but the local shop didn't have a replacement listed in their system and I had already ordered the new HVECU by then so I didn't mess with it further.

Anyway thanks a lot everyone, Prius lives on!