Hybrid Water Pump, Second Failure in 6 months

I would find a new mechanic. P0A37 does not mean your inverter water pump failed and C0547 does not appear to be a valid code for the Gen 2 Prius.

There is in fact no code that means your inverter coolant pump has failed but there is a code – P0A93 – that sets if the inverter is getting too hot and usually indicates that your coolant pump has failed.

It is easy to verify - put your car in IG-ON (two presses of the power button with your foot off the brake) or make the car READY. Then take the cap of the inverter coolant reservoir and look at the coolant. If your pump is still working you should clearly see coolant moving. If it is still, your pump is not working.

Pump failure is not the only reason for the pump not working but it usually is. Test the pump to verify before buying a new pump seeing as you (were told it was supposedly) recently replaced. It is very unusual for an OEM pump to fail so soon. If it has failed there is a 12-month warranty on the OEM pump so it should be replaced on Toyota's dime.

 

Where are they getting the water pump from

 

Jane,

Assuming they used a hybrid capable scanner and correctly read this code,
A P0A37 is Generator Temperature Sensor Circuit Range or Performance, which is a temperature sensor located inside your transaxle.
There are 2 possible subcodes associated with P0A37:
Subcode 258 which is #2 Motor Temperature Sensor Malfunction
Subcode 260 which is #2 Motor Temperature Sensor Performance Problem
Your possibilities are either a transaxle temperature sensor problem or the transaxle fluid is low. There is no dipstick for the transaxle, it just has a drain plug and a fill plug. Checking level requires removal of the fill plug. With the car level, fluid level should be even with the bottom of the plug hole. That's the first thing I would check. Or, I would just get the fluid changed and document how much fluid drained out. Off the top of my head, I believe it should hold around 3.6 quarts.

If the temperature sensor is actually determined to be faulty, the repair manual says the transaxle should be replaced because this sensor is not available as an individual item. Luckily, the repair manual also says this alarm triggers the master warning light, but the car should remain drivable.


If the shop is using a generic scanner, it could be reading any hybrid system codes incorrectly. It wouldn't be the first time.

 

Yeah could be counterfeit pump.

 

My mechanic thinks it failed because it had to work overtime when the hybrid battery was dying, in addition to the blocked vent.

Absolutely wrong. The inverter cooling water pump runs off the 12 volt system. The HV battery could blow up in a fireball and it would have no direct impact on the condition of the inverter cooling water pump.

Unfortunately, these pumps should almost be considered a wear item and replaced ~every 80k miles. It would help prevent being stuck somewhere. Unfortunately also, most dealerships charge around $600 to replace this pump. They can be purchased from a Toyota dealership for about $150 and installed in about an hour by anyone with a bit of mechanical ability, just by removing the driverside headlight. I HIGHLY recommend using only a Toyota pump. Aftermarkets tend to be of poor quality. If your mechanic is getting one from the local autozone or whatever, you'll probably be visiting the mechanic again soon.

Toyota part number G9020-47030 or 47031 (most recent version). The ones on ebay, etc that are like $40 are Chinese counterfeits.

Unfortunately, if you look up those part numbers, even Toyota mislabels them as:
Engine Coolant Inverter Water Pump Assembly
This pump has NOTHING to do with the engine coolant loop, so this only adds to the confusion.

Your mechanic sounds like he has minimal knowledge of a Gen 2 Prius. Please make sure he replaces the inverter cooling water pump and not the engine coolant pump, coolant storage pump or the pump that moves coolant for HVAC. As mentioned, the inverter cooling water pump is located directly behind the driver side headlight. You can use 2 medium sized plier style hose clamps to pinch the inlet and outlet hoses, remove and replace the pump, and only lose a couple ounces of fluid.

 

G'day Jane,
You also mentioned the dash cluster is "going out." Yep, that's a known failure of the gen 2 Prius and it can be pretty annoying or worse. The fix is to extract the sub assembly that has the display and electronics with it by disassembling the dash and a bunch of the interior of the cab. (blah -yeah takes space and patience) And then taking the board to your electronics bench changing the small $0.50 part or sending t to someone who will do that for you.

The dealership will charge you ... a fair bit. I would hazard a guess at $600-$800, but get a quote because that is a WAG (wildly assumptive guess).
However, these are all skills you can develop yourself and the tools are not super expensive or exotic. Youtube has a lot of guidance on this topic. It is a way to build self reliance, but maybe not the first DIY automotive thing you want to do. Changing that water pump is easier, for example, but potentially more messy.
The bright side is that once you do this particular fix, you should not have to do it again in the lifetime of the car. (unlike the water pump)

I do recognize that not everyone has space, time/patience to do this sort of work, but if you do, I encourage you to go for it. You will have more than a sense of accomplishment when you are done.
(besides I live far enough away you are not gonna come park it in my driveway and say, "HELP!")

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