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The 12-volt battery replacement was not the final chapter in our recent repair saga.

Several days later, more errors (including the "Hybrid System Malfunction" icon) appeared on the MFD screen. Since these indicated a hybrid system failure, we took our 2002 Prius to the dealer for troubleshooting. With over 70,000 miles on the odometer, we were actually hoping for a hybrid system-related problem, as the regular warranty had expired.

It turns out that the inverter water pump had failed, and the inverter was overheating:

P/N G9020-47021, pump assembly, water w/m = $133.75
Labor to remove & replace = $149.00
Shop supplies & sales tax
Approximate total = $300

The error codes included "P3130", which appeared "due to the inverter running hot"; and the inverter was replaced, per TSB/EG022-04:

P/N G9200-48071, inverter assembly w/con = no charge ($3,500.00 list)
P/N 00272-SLLC2, super long life coolant = no charge
Labor to remove & replace = no charge

Our Prius is back to normal. I feel lucky that this failure occurred now, before the hybrid warranty ran out; and that our total repair cost was only about $425, which includes the 12-volt battery we replaced a few days earlier. Actually, five years on a 12-volt battery is considered "long life" in Arizona. They usually only last about two or three years in other cars, due to the heat.

I got the old water pump back, so I will know what to look for when it fails again. Hopefully, next time I can replace it myself BEFORE the inverter fails (after the hybrid warrantly runs out). I haven't looked to see where it goes, but it looks simple to replace. However, it is probably buried somewhere deep inside or under other parts that will have to be removed.

I had only read of one other pump failure. It was in Honduras and I had tracked down the replacement part from metro tpn for about $100.

Replacement of the inverter may have not been needed, but since gratis there is nothing to complain about there. I see you have now been changed over to SLLC coolant, as used in the new model Prius.

Is is always possible for air bubbles to remain after this coolant change. You should put Prius in 'ready mode' and look under the hood. The inverter pump is now running; see how the fluid appears in the top reservoir. The front part of it should be at a distinctly higher liquid level than the rear, an indication of correct function. If you do not see this difference, it means that air bubbles remain in the system and must be removed. Please keep an eye on this over the next few weeks.

DAS

Too bad the cars were never provided with a coolant guage making this easy to spot. Obviously the coolant idiot light must be set extremely high.

This makes a case for the ScanGaugeII which can be set to indicate real-time coolant temperature as well as three other readings and trip statistics.

I've been considering a ScanGaugeII - available for $150 in the PriusChat store. The ScanGaugeII would also work for the previous model Prius, like the 2002 posted here.

I have a Scanguage II and I don't think you can get inverter temperature
with it.

You mean inverter coolant temperature? Dan can probably explain if it is a different coolant system from the ICE.

Yes, the inverter has a separate coolant system from the ICE.

The inverter water pump is electric (12-volt) and is about the size of your fist. It looks kind of like a miniature washing machine pump or hair dryer that might cost about $15 at Home Depot. However, one has to remember that it is cooling a $3500 hybrid inverter module, so you have to multiply that by about 10x!

It seems like this is a critical part of the hybrid system, since its failure can result in repairs that will make you seriously consider whether it was wise buying a new-fangled hybrid. But, it is not covered under the extended hybrid warranty.

I guess in the big scheme of things, $300 is really insignificant, considering I have paid for absolutely no repairs on our Prius in the past five years, except for gas, routine maintenance (oil changes, etc.), one set of tires, a gas cap, and shotgun-troubleshooting for one "failure to start" incident in Flagstaff. (Luckily, a call to our local Phoenix Toyota dealer said to have the Bozos in Flagstaff reset the codes and get the heck out of there FAST!)

In all, it has been an extremely reliable car; and it's repair history is only exceeded by our 1998 Camry.

And probably my 82 Chevy pick-up!

An inverter overheat should certainly have been flagged with a DTC, and before the inverter was damaged. Thus I suspect like DAS, the inverter replacement probably wasn't necessary. But hey, it was replaced at no cost to you, so no problem there.

Very interesting saga. I guess I'll have to remember this for future reference as well before the hybrid warranty runs out.

It's probably partly because the 12 volt battery is in the trunk as opposed to the normally very hot engine compartment.

Had Inverter water pump replaced today in 04 prius 62000 miles after recieving like 5 different warning lights on car I took to dealer, had service guy said go ahead and drive because he thought it had to do with me exiting car while running with smart key outside car...he said it would clear after 4-5 weeks...but after driving home with warning lights on I couldnt take it and took it back to dealer and had Diagnostics ran and they found the waterpump problem with 3 of the lights pertaining to the smartkey

Sorry for waking a zombie here, but here's the thing.
A week ago I replaced my classic Prius's low-voltage
battery and now I'm having P3130 inverter water
pump issues.

Do you think that replacing the 12v battery, or the
conditions that exist when it needs to be replaced
could be kill the inverter water pump?

I'm not absolutely sure that mine is dead, but after
reading this page I'm leaning that way.