Water Pump Relays and Fuses

Hello!

I have been stalking this site and using all the great information here to do many repairs on my 2010 Prius since 2017. So thanks for all the help already.

What I am currently struggling with, I can't seem to get the info I'm looking for. Bought the car used with 217K miles and currently has 267K. Got the P261b error code and car glided to a stop at the side of the road. Had it towed home, ordered a new AISIN water pump and thermostat from Amazon which are arriving today. Old one was removed yesterday and it still turns though not smoothly. Was hoping it was dead seized.

From what I have read here, water pump is the probable cause though I should have checked relays first. I have been struggling with diagrams showing relays from the Chilton's Library through my library and other diagrams online. The problem I am having is deciphering which relays marked "Cooling" or "Fan" are for the Cooling system (which I assume these would be) and which ones are for AC cooling. Can anybody point me to a document or thread in which the relays and fuses on the 3rd Gen Prius are defined? Or even a source that shows a diagnoses from start to finish when dealing with P261b (ie. Step 1, Check relay R1... etc).

Thanks in advance!
Jason

 

I would love to have access to the repair manual for this car. But I don't.

The reason I asked the question in the first place was because the new pump and thermostat and coolant ended up costing around $300. I wanted to know, before putting these in, cheaper steps that could be troubleshot beforehand. I love a good step by step troubleshooting guide, but I can't seem to find one for this problem. Like I said, just a list of which relays affect the cooling system would be helpful. From diagrams I've found online, it seems to be at least R1, R2, and R4. But there are also several fuses labeled "Electric cooling fans" which could be anything.

Luckily, when the new unit arrived, there was a noticeable difference in the way the propeller spun vs. the old unit, so I went ahead with the exchange. So far, the code has gone away but the outdoor temps here are in the mid 20s so the engine fans are not kicking on. The temperature from my scangauge got up to 180F. I think I read in another post, Chapman, that you said they should kick on at 95C (approx 203F) so I'll have to drive it more and see?

Thanks for the support!

 

Drove the car for over an hour yesterday and temp stayed within180-190. So, all good there. Thanks for the temp warning, I will continue to keep an eye on that while driving, especially as the weather warms up! Isn't there a scangauge setting/OBD reading that monitors if the thermostat is open or not? I'll have to look into that to watch too.

Lol, we're too sedated on hamburgers and Jesus in Kansas to secede. Believe it or not, I looked at most of the sources on the Elektroingenieur post before I posted here, even downloaded and combed through a few but either they didn't have what I could use or I'm not smart enough to read them. When I searched the techinfo site, no repair manual came up. Just owner's manual, quick reference, USB guides, etc. I didn't create an account, so maybe I need to do this? If so, from the looks of it, they charge for the repair manual?

Not sure what you mean by a "three-fer" (sorry). Do you mean fuses 36,37,38 as a single fuse? Of which in the photo the bottom is in line with the bottom of the oscilloscope? Those three are labeled "CDS Electric Cooling Fans, RDI Electric Cooling Fans and HTR Air conditioning system."

In your photo, the two blue relays at the top right (R2 and R4) are "Cooling Fan" relays with R1 (hidden behind the oscilloscope) labeled "Cooling System (ENG W/P) and R8 (the rouge one at the bottom right of the box) also labeled "Cooling Fan (Fan No.2). Are these the 4 you are referring to?

So the question would be, between the "three-fer" fuses and the 4 relays, is that the total of all relay/fuses connected to the engine cooling system? At this point, I'm asking for anyone who might stumble upon this post. You are right, I put the pump in and the code went away and everything seems okay at this point for me. But if I would have known what relays/fuses to check before dishing out $300 (and a few days of very cold labor) I would have done that first.

Thanks for your help!!

 

Missed that, but $20 for 2 days usage...

The Alldatadiy seemed like a better deal but their prices have changed: $60 for a year, $130 for 3 years.