The P314A was coming on in my newly purchased 2010 Prius Base Model. 175,000 Miles. Read Forums and watched Youtube and immediately replaced the inverter cooling pump (and also did the gasoline motor water pump because it looked shot (original). However, still have the error. Can reset it with my Autel Basic Scanner but it comes right back. I've checked the fuse but does anybody have the wiring diagram and connector pinouts so I can try to see why the new pump is not going on. I would have still replaced the pump given the general condition of the car (appears somebody just was "Gas and Go".) but now need to find the "Real Problem".
I found the wiring diagram and all the cooling circuits (fans, Gas Motor Water Pump, Inverter Water Pump) are fed by a common relay. That relay was bad so I replaced it ( swapped it with headlamp relay and the headlamps stopped working). Problem went away for a day but is now back. I purchased a warranty with this car so am taking it back to the dealer for them to diagnose. Thanks for the responses and inputs.
A 3rd gen for sale at those miles is likely to have a failing head gasket, if the EGR components and intake manifold have not been cleaned. To get an idea of the EGR condition, see video #16 here: Nutz About Bolts Prius Maintenance Videos | PriusChat
Thanks for all the advice. Still have this intermittent problem after Toyota Dealer supposedly troubleshoot. Their solution - $4200 for a new Inverter. Thanks but no Thanks. I found the following factory manual troubleshooting procedures which look very helpful. Please pass around as I know others have had the same intermittent issues that pointed to the Inverter Cooling Fan. I'm guessing my issue is an intermittent wiring issue as others have speculated. Mendel Leisk - Thanks for the advice on the head gasket and EGR. Head Gasket leak test passed (Fluid did not change color from Blue to Yellow/Orange). However, I have the low speed/low load EGR Rattle. Will need to take that apart (along with the compression test, borescope, and plug replacement).
That sounds like the test for exhaust gas in coolant. That tends to not be the failure mode with 3rd gens; it's more likely to be coolant leaking into cylinder, typically cylinder one or two. Leak-down test and or boroscope inspection of the cylinders (with the coolant system pressurized) are good for checking for that failure mode. Is engine coolant level stable in the reservoir?
Engine Coolant is stable in the reservoir. Only have about 1000 miles since purchase, need to monitor longer. No oil use yet. Plan on changing oil at 3,000 since purchase. Oil looks new, very little carbon fouling. No signs of water or other fouling. Inverter fault has magically gone away. Very strange. Expect it to be back. It seems related to a wiring issue around the relay/fuse center. May need to take it loose and inspect wiring below. I'm a little surprised that the Toyota Manual and other videos suggest wiggling wiring and trying to get fuses to pop or things to stop working. Plan on doing it though. If anybody knows of a Fuse/Relay center inspection/troubleshooting video - please feel free to forward. Prius from Hell (Car's Nickname) is my primary transportation right now, but plan to do a major push after I get my wife's car back from tranny shop. Take windshield wiper section apart, do compression test, maybe leak down test, borrescope, clean Intake Manifold, EGR Cooler, replace EGR, Change PCV, do a couple of rain dances and maybe tea leaf readings. This whole thing is an experiment in cheap motoring. Can I get this thing refreshed and get it to 300K (from 175K) for a reasonable amount (depreciation and maintenance cost) doing all the work myself. Can you expect to get a used Prius to 300k that has not been pampered ????
