inverter pump failure highlights moronic display design

Yesterday we took our 2007 Prius out to run some errands. It was very hot (100F). Drove around on city streets for 10 minutes with no problems, but a mile or so after going on the highway the red triangle of death appeared. Pulled off at the next exit and consulted the manual. It said to take the car to a dealer, but gave no further information. The day before I drove it 7.5 miles each way back and forth to work with no problems, all on city streets and in the cooler part of the day. Before that we had been away for 8 days during which time the car sat in our driveway with all the windows down an inch to keep it as cool as possible, but not driven or even started. It was very hot during that time too, so I figured that the battery might have gone out of balance during the extended period of heat and nonuse. On returning home with the red triangle on the car sat for about 15 minutes not running and then TechStream was used after pushing start twice without my foot on the brake. It read code P0A93. So the inverter pump, not the battery. Ran the health check (S309-04) and found these temperatures (F):

Inverter temp MG1 198
Inverter temp MG2 176
Converter temp 189
Engine coolant 189
Ambient 102

What is the trigger temp, 210F? Seems like it may be set awfully high.

Checked the tank next to the inverter and no motion at all. Not even if the car was turned on normally. Fuse AM2 is not blown.

So it looks like a failed inverter pump. Fine, they are known to be less than reliable, and maybe it was coincidence, or maybe sitting for 8 days let something settle out and jam it up. I will get it fixed on Monday.

My real gripe is with the display. It popped a red triangle of death in the upper left corner of the MFD in addition to the one on the dash. Touch the symbol on the MFD to find out what the problem is, right? Wrong. The thing is too stupid to provide any useful information. Neither is there a way to monitor any of the relevant temps without running TechStream (or equivalent), the car will not display this information itself. I can only assume that the temps were already well above normal when driving around before the triangle came on, probably the same the day before, but not so high as to trigger the dash warning. Twice on older cars I have caught cooling system problems by noticing the car was running hotter than normal, but not yet boiling over. (One was a failing water pump, the other a coolant leak.) On this exceedingly complex car this crucial information is completely hidden from the driver. A cynic might wonder if Toyota designed the display specifically so that it would convert low level failures which could be repaired proactively (the inverter is running a little hot) into expensive repairs (inverter gets cooked, give us $4k)!

 

Parts department at Toyota Pasadena quoted $199.62 for the part, and none in stock. Going to see tomorrow how fast my usual mechanic can get it done and what he would charge.

I wasn't complaining about the pump breaking, that was not unexpected, I was just annoyed that the car provided so little information about what had failed - when it has this information readily available. If this is typical of failure scenarios when the ICE water pump fails it does what - light the triangle (or some other obscure symbol) on the dash and then shortly thereafter the car stops dead when the temperature gets really high?

 

Do we trust used inverters? I hope so, because replacements from Toyota are a lot more than that. At this point I don't have any evidence that the inverter itself is damaged.

 

Minimally it could have put the error code(s) on the MFD (obviating the need for a separate reader) and then listed what they meant in the user's manual. No question in my mind that the 2007 tech would have been able to do that. Not quite as convenient as putting the text on the MFD would have been, but it would only have needed a small amount of software to retrieve and display the error code, and not a lot of storage to hold the description text (possibly in several languages.) The resulting "pull over and look it up" would have been a vast improvement over the actual "what the heck does that mean"? That lack of a temperature gauges is pretty much inexcusable. Come to think of it, they could have replaced whatever software currently puts the error icon on the MFD with that which shows the actual error code(s) and the total software size might very well have ended up smaller. Heck, even something like Honda's blink codes would have been better - so long as the meanings were listed in the user's manual.

 

Took the car to my usual mechanic but he couldn't get a replacement pump from Toyota - they are on back order until who knows when. They wouldn't even estimate a delivery time. So I ordered a Dorman unit from Rock Auto (just under $80 with tax and shipping), which should be here fairly quick if they stock it in the warehouse near L.A., otherwise a few days longer. However, my mechanic doesn't want to do the work - his experience with nonToyota units has been that they fail very quickly. So it looks like I will be doing this myself after all.

While I'm waiting it would be good to verify that 12v is actually getting to the pump. The AM2 fuse is good but I suppose the relay feeding the pump might have failed. The picture of the pump I ordered:

More Information for DORMAN 601015

appears to show a two pin power connector with some type of squeeze release on right side (in the picture). How much of the car needs to come apart to unhook that connector in order to get a voltmeter onto the corresponding slots on the plug? Alternatively, I have a computer power supply which could supply 12V which could be applied to the existing pump, but I don't know which of the pins in that picture is +12V
and which is ground, nor how much current it needs to run. The PC power supply won't work if it needs a whole lot of amps.

Finally, in this video

VIDEO - Gen 2 Prius inverter water pump P0A93 - Luscious Garage | Hybrid Specialists

from Luscious Garage they replaced the pump by tilting up the inverter rather than removing the bumper and headlight. That looks like a much better way to do this. Unfortunately there are some mysterious out of camera view actions at the beginning. Anybody seen a write up of what they did exactly?

I don't have the shop manual.

Thanks.

 

Watched some of those. Taking the driver's side headlight out does look like it provides the clearest path to the pump. Pretty sure I could get one of my skinny hands down to the pump even without removing the nearby inverter bracket, but to get both hands in there, and to see what I'm doing, that headlight has to come out. (It looked to me like in the LG video the mechanic was doing a lot of it entirely by feel.)

 

Thanks for the offer but I think I'll just put the new Dorman unit in myself.

I wonder how long our pump may have been out. Last night the CEL was reset and today the car was driven to work - no CEL reappeared. Maybe it will come on going home tonight, when it will be warmer. If not, the pump could have been out for weeks, because it has been nearly a month since the last time the car was on the highway (and even then it was only 70F).