(im)Famous "Check Hybrid System" on highway - P0A0F and P261B upon diagnostic

Hello all, first time long time.

I have a tendency to be long-winded so I'll make an active effort to be concise. On the interstate driving home from a work trip this past Friday I got the famous "Check Hybrid System" message accompanied by a beep and the apparent shutting off of the ICE. Power steering / brakes / etc thankfully remained operative so I safely exited the freeway and coasted to a safe area.

Upon restarting, the message persisted and (I think) the car would still not start. I was a bit stressed and could possibly be mis-remembering this specific part. Ended up locating the procedure for clearing this message by turning the car on-and-off three times in rapid succession via the start button. This made the message go away but the check engine light persisted, as well as the TPMS light, which had come on a short while before despite the air pressure being acceptable in all four tires.

There were no good options so I rolled the dice and drove about 200 miles home and made it safely. The car acted pretty normal the rest of the way though I took it extremely easy, to everyone else's dismay I'm certain.

Took it to the local dealer first thing Sat morning and I was returned two diagnostic codes: P0A0F and P261B. Recommendation was to replace the Purge Vacuum Switching Valve (they referenced TSB-0041-15) and the engine water pump. Total cost: $1400 and change. $1000+ for the pump and $400+ for the VSV.

Here is where my doubts / cynicism kick in. I can't quite work out in my head how the engine water pump is causing the "check hybrid system" message and accompanying engine shutoff? I've never received a high-temperature warning, but wouldn't that be the logical fallout of having an engine water pump that is not circulating enough coolant?

Is anyone aware of a scenario in which the water pump would cause or contribute to the issue described above? I can stomach paying for the VSV since replacing it involves resetting the ECU and I don't have equipment or inclination to do so myself. Adding the water pump as well hurts a lot more.

Some particulars in case they are relevant:
2010 Prius III. 127,000 miles.
Oil changed just days before incident (0W-20 synthetic). No prior issues / accidents. Basic maintenance only up to this point.

 

Cheers for the response and welcome.

I replaced the 12V about three years ago. Current voltage is a steady 12.8V (checked with my multimeter via the positive terminal in the engine compartment fuse box) with no load. I think it's good.

I'm aware that the 120,000 is due and it's on the radar, however this issue will take precedence for the moment. Do you think they are related? I didn't see anything on the 120k maintenance list that would directly address either of these issues unless it was caught under "inspect exhaust system" or "inspect engine coolant"?

 

Thanks for the reply. Yeah I'm tempted to do the pump replacement myself, but I think we may be on slightly different pages regarding the error message. Do you think the pump failing would cause a "check hybrid system" message and, further, do you think it would be possible to drive over 200 miles on the interstate with no engine coolant circulating due to a failed pump and no engine overheating lights/messages?

The service guy seemed to think that it's possible that the P261B code had been sat dormant for a while without triggering the check engine light and only popped up due to us running the diagnostic but I have no clue how feasible that is.

I do note that the VSV is quite inexpensive and easily accessed, however it would require resetting the ECU if replaced, correct? Is that something easily done outwith the dealer or expensive tools/software?

Possibly. I've obtained a couple of alternate quotes for doing the same work and they're both $1000+ as well. Probably paying MSRP for the parts, which is $600+ for the pump and $112 for the VSV then hitting me on labor. I see where the cost is coming from, it's just tough to pony up for the pump replacement if I can't be reasonably certain that it's contributing to my problem.

Cheers again for the reply.