Coolant pump B control malfunction (P261B)

DTC P261B means that the engine coolant pump has a problem - not the inverter coolant pump.

You can try to touch the pump while the Prius is READY to see if you feel a vibration which shows the pump is functional. If you do not feel this, then you will need to replace the pump.

 

Find the engine coolant pump at the front of the engine (which would be facing the driver's side fender with your Japan domestic market model) and see if you feel vibration when the Prius is READY and the engine is not running.

 

I recommend you research the correct part number on toyodiy.com to make sure Japan domestic market vehicles use the same pump as North American vehicles. The North American pump MSRP is USD565 and the discounted price is ~USD400. Part number 161A029015

Regarding online sources, there are several good ones. For example,

parts.com
Camelback Toyota (Phoenix, AZ)
AutoNation Toyota Gulf Freeway (Houston, TX)

 

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I am unsure where to post this as I am new to the forum/website. However, about 2 months ago I drove to a store, spent about 2 hours there, and then when I came back it had all sorts of messages on my 2010 Toyota Prius. Mainly, it said check parking system as it is on uneven surface.. .. not quite that language but something about this. I took it to my local dealer and they said the ECU had been fried, my 12v battery was dead and not working, and a fuse had been blown. Ultimately, I had my 12v battery replaced (I had replaced it a year earlier and had a warranty on it yet), replaced my ECU, and replaced the blown fuse.

Then less than one month later I had a "check hybrid system" light come on along with the bright orange triangle caution light, and the check engine light. Ultimately, I took it to the same dealer who said a code P261B came up and a different code regarding my intake engine manifold. The dealer said I needed a new engine water coolant pump and recommended I replace the engine manifold because, as they said, it cannot be cleaned but only replaced. Yesterday, I spent about $800 to replace the electric engine water coolant pump. I did not do the intake engine manifold because that was going to cost another $600, which I do not have. I picked up my car today, no check hybrid system light nor any check engine light. I drive approximately 20 miles and then later tonight the check hybrid system" light come on along with the bright orange triangle caution light, and the check engine light all reappear.

When I got home and parked my car I looked inside my hood and saw my engine inverter coolant level was right at the low level. Could this low level engine inverter coolant cause all of these lights? If not, any recommendations or suggestions? I am, obviously, taking my car back to the dealer tomorrow. This is turning into a three month, >$1,600 ordeal so any help would be appreciated!

 

I was at Toyota getting my 2010 Prius checked out because my Prius suddenly got check engine light came on and the car could not accelerate.
The service person said it had a code P261B. I specially said which pump has the problem because there are two cooling pumps. One for the engine and the other is for the inverter. He said the code came up for the engine cooling pump but the actual problem was the inverter pump. The inverter pump part number is G9040-47090.

 

mars23mj,. Did you change inverter pump and the problem was gone? Let me know I have same code P261B after changing OEM WP and Thermostat.

 

It's too bad a service person would spread nonsense like that. P261B is definitely about the engine water pump; you can see how the pump is controlled here, and you can even mess with the signals and make a P261B come up on purpose if you need convincing.

There's no accounting for what the service person said to mars23mj. In some cases there's also a disconnect between what the service person said and really did. Maybe the service person changed the inverter pump, the engine pump code didn't happen to come back, and that was counted as solving the problem. You can, of course, proceed the same way ... but it is better to pay attention to what the codes mean.

You might be curious whether there is a code for the same condition, a suspect pump speed reading, but for the inverter pump. There is; that code is P314A.

 

Thanks ChapmanF! I am getting this code after changing WP and Thermostat. No code when driving below 45mph at all. Coolant staying at 195-200.

If I take her >55/60mph, coolant shoots up 220 and P261B.

 

Stop driving the car until you flush the coolant sysytem and make sure nothing is clogging it.

The spin your water pump and see if its smooth or not.
If its not spinning freely then get a new one.

Otherwise slap it back on after the flushing and put two gallons of coolant back in.

The thermostat is fully open at 204F and you do not want the engine to be in that temperature range for very long.

Fix it fast before you blow your head gasket due to overheating.

http://www.RedBullet.net

https://ProjectLithium.com/?ref=mG0GE

http://www.Pulstar.com

http://www.PlugOutPower.com
Use code 7373

http://www.hybridpit.com
Use code azusa

http://CatStrap.net
Use code azusa

 

That sounds familiar. Maybe you've mentioned it in another thread?

So the P261B means that the ECM's reading of the water pump RPM looks too low. The ECM gets that reading electrically, over some lengths of wires, from a tachometer signal generated in the pump (the details are in the thread I linked to above). So there are places, plural, for stuff to go wrong.

So obviously the code doesn't necessarily only mean the pump has to really be turning the wrong RPM; other possibilities naturally include the pump being ok and the tachometer signal getting messed up on its way to the ECM, one way or another. The ECM itself hasn't got any way to tell which of those possibilities is really what's happening, so there is good honest work to be done by whatever human will be diagnosing the issue.

Data on the pump target speed and measured speed from a freeze frame when the code was set might be useful information, as well as the electrical tests indicated for the circuit. It is easiest with an oscilloscope to see what is going on, but another poster very recently found a problem in his pump wiring successfully with an ordinary multimeter.

 

I have a brand new water pump and coolant was flushed during the new water pump install. how to make sure nothing is clogging? when I drained the coolant from the radiator it was flowing freely. FIY, I just bought this car.

 

Yes, I was asking the same in another similar thread. After 25mins in maintenance mode coolant temperature goes to 204f. I turned it off.

 

what is the normal coolant temperature range at 75 mph cruising?

 

Would you object to the idea of finding out what's causing the P261B and fixing it?

 

I am trying to find root cause for P261B. Its a new W/P just installed 3 days ago. So I am not sure where to start again.

 

Normal operating temp at those speed is 180-190F
Except on an incline where it should not go over 204F

http://www.RedBullet.net

https://ProjectLithium.com/?ref=mG0GE

http://www.Pulstar.com

http://www.PlugOutPower.com
Use code 7373

http://www.hybridpit.com
Use code azusa

http://CatStrap.net
Use code azusa