2004 Prius won’t start up. Died while driving. Warning lights blink then shut off.

Suddenly, my 2004 Prius won’t start up. Died while driving.

When I hit the Power button, the warning lights blink and then shut off. The squares around the gears (R, P, D, B) on the display blink after the other lights turn off. When I hit the Power button the light on it is amber and it blinks 8 times and then the 9th blink is like a half blink. The Power button blinking starts when I hit the Power button and continues even after all the other lights are off (including the illuminated gear squares).

2004 Prius
HV battery replaced a 221 miles ago
12v battery new from Toyota in November
250,000+ miles

I did a voltage test using the screen on the vehicle and the diagnostics page and it’s at 12.3 volts. The car died while I was driving and made no indication of a 12 volt failure before it died (dimming lights, warning lights, etc.), it just straight up died.

When I enter auxiliary mode, the monitor screen lights up and the radio and clock work, but when I hit the Power button again in an attempt to start it, the display lights blink as described above and everything shuts down (including the monitor screen w/ radio, clock).

At this point, I decided to disconnect the HV battery and repeat the above steps. I found that the vehicle did exactly the same things as mentioned above: quick flash of display, blinking boxes, car doesn’t start. So the vehicle is failing in the exact same way when the HV is connected and disconnected.

I spoke with the technician at the company who replaced the battery and they said it’s not likely that the problem is the HV as the system is not firing up long enough to cycle through to the point of access the HV battery.

Perhaps there was an issue with the communication between the vehicle and the HV battery?

Could it be that I have an ECU/PCM problem? A problem with the Body Control Unit?

If any of y’all have any suggestions on what I can do to figure this out and fix it, please let me know. I hope to get this car back up and running as I love that li’l thing. Thanks for your help with this matter.

Thanks in advance,
-Bob

 

FWIW, I found this other thread where the OP had similar, if not identical, problems:

Prius won't start, flashes the combination meter for a split second | PriusChat

The thread was abandoned without a stated resolution, so I started this thread. I also went ahead and posted over on the other thread in an attempt to revive it.

It's ALIVE! The other thread. OP came back and posted that the fix for them was replacing the ECU. I've been suspecting that this is the problem and will give it a shot. Will update when I finish the swap.

 

I have, but it won't scan in Aux mode and won't turn on long enough to scan otherwise.

 

When I hit the button a second time (w/out foot on brake) it turns on and off again in the way described above. Same as when I do have my foot on the brake and press the Power button.

 

Well, that wasn’t the problem. Or wasn’t it?

I bought a used ECU from eBay and put it in today. The car turns on for a split second and then back off, as described in the original post.

So, either the ECU wasn’t the problem (and I, once again have no idea what the problem is) or the used ECU I bought is broken in the same way.

It might seem unlikely that the used eBay ECU failed in the same way as the original but I did once buy a used ABS actuator for a Gen 1 Prius and put it in (huge pain in the rear) only to learn that it did not work at all and wouldn’t even power up. So, it happens… ugh.

If anyone has any ideas or suggestions, I’d appreciate it.

Thanks.

 

Well, what do ya know?

I checked the AM2 fuse and it’s blown. Swapped the fuse and unplugged the inverter coolant pump and it started right up. Plugged the inverter coolant pump back in and started it up. Started smelling burny and smoke wafted up from the inverter coolant pump. Turned it off and ordered a new inverter coolant pump. Sounds like this was the problem all along. Ill update when I get the new inverter coolant pump in there.

Thanks a bunch for the tip, mr_guy_mann!