Capacitor issues, other than the MFD?

It is common for the MFD to fail because an electrolytic capacitor used by Toyota wasn't quite the right capacity and over time it degrades to the point where it cannot do its job. That was a design failure, even though it took a few years to show up, it wasn't really the typical sort of capacitor age failure.

These cars are getting up there in age, mine will be 20 next year, and at that age it is fairly common for this type of capacitor to fail. They swell, leak, or just get so far out of spec that they cannot do their job anymore. This can cause big problems in a car if it happens in the ECM. However, it seems not to be common in the 2nd Gen Prius, at least yet, as I have no recollection of any posts here describing an ECM failure from capacitors aging out. I have never opened a Prius ECM. Did Toyota just use really high quality electrolytic capacitors (in which case they will fail eventually, it will just take longer) or did they employ solid state capacitors, which last much much longer than the electrolytic ones?

 

The MFD is definitely going to be hotter, but the ECM is tucked up under the dash too. However, it is a little lower and is in a metal box which is bolted to other metal which might keep it cool by diverting heat down into the frame of the car

I looked for a picture of a 2nd generation Prius ECM board on Google and didn't find a single one. The only failures I have seen referenced were of the "external short to ground kills ECM" variety.

 

Maybe the Gen 5 issue is somehow related to its high parasitic draw issues? If that box of caps is being charged and discharged too often it could cause them to fail sooner. Just speculating, I have no data to support this.

The capacitor plague (huge number of defective electrolytic capacitors) came to an end a year or two before the 2nd generation Prius did. Now admittedly most of those failed caps were not from first tier manufacturers, but if a particular generation Prius was going to have capacitor problems it would be more likely the 2nd than the 5th. Toyota seems to have avoided this problem by sticking with first tier Japanese made capacitors for the 2nd generation. I suspect Toyota remains to this day very picky about whose capacitors they use. Although I bet they have phased out electrolytic capacitors everywhere they could in favor of solid capacitors. For instance, in this disassembly of a 5th gen inverter

I did not see a single traditional electrolytic capacitor (the sort that have a pressure release on top, and are noted for bulging and leaking). There were a lot of capacitors which look (at this low video resolution) like the solid ones used on Gigabyte's ultra durable motherboards (and by other manufacturers):

https://www.gigabyte.com/webpage/8/article_02_all_solid.htm