P261C engine coolant pump b control circuit ow, what does this code mean

not sure that is a correct code, are you using tech stream?

it could be that you need to replace the 3 way coolant control valve

 

check the inverter fluid reservoir with the car in ready. there should be movement in the fluid

 

The "someone" is correct. Stop driving the car. Replace the electric engine coolant pump.

 

You need item 8, see exploded parts diagram here:
Water Pump for 2011 Toyota Prius | AutoNation Toyota Gulf Freeway
The part number is 161A0-29015 and it is pretty expensive, USD 621 list price.

The US amazon.com website shows the Aisin WPT-190 pump here for USD262. I would use that pump instead of the Toyota pump.

 

It's not a bad idea to add the thermostat to this job. It's positioned directly opposite the engine casting where the water pump mounts and only adds 35 USD to the job:


2011 TOYOTA PRIUS Water inlet sub-assy, w/thermostat. Inlet sub-assy, wate - 1603137010 | Toyota Parts Overstock


I did a preemptive engine water pump replacement on my late, great 2010, using the Aisin WPT-190. It is indeed the oem pump, with the words Toyota and Aisin actually ground off. You can view the grindings in this pic and Youtube video:

 

It's always best to replace the thermostat when you replace the water pump. And to back flush the system.
It really can't hurt.

 

P261b is engine water pump failure
P261c is no power to pump. Check fuse first second check connection

If you have p261b do the work yourself. It's pretty easy and save a lot of money. Buy oem part on eBay/Amazon. Check YouTube for installation guide.

 

Just got this today when I was on my way home. Going to check to see if the cable has disconnected or the water pump has seized.

Ordered a new pump just now just in case.

EDIT: I replaced the engine water pump. could this be the inverter water pump?

 

The description of code P261C is "Short in Coolant Pump "B" Control Circuit "

Possible trouble areas are:
- Short in water pump assembly circuit
- Water pump assembly
- ECM

 

Coolant Pump B, that's the inverter.

Well have one on order.

 

Code P261B and P261C are for the engine water pump, not the inverter pump.

 

Says who?

P2 codes have descriptions that are standardized by SAE; when there are P2 codes that pertain to what Toyota wants a code for, they use the ones SAE defined. Per SAE, all of the P261{B,C,D} codes pertain to a "coolant pump B", and Toyota has used those codes in the engine control module to report problems with the engine coolant pump.



The detection condition for P261C is "Water pump output voltage is less than specified value while the water pump assembly is operating (1 trip detection logic)", and interpreting that sentence requires thinking about whether a water pump output voltage is a thing and, if so, which circuit carries it.

You might at first think the pump's RPM feedback signal might be an output voltage, but it's really a pulse train, produced by the water pump pulling down a voltage supplied by the ECM. The how-fast-to-go signal from the ECM to the pump is also a pulse train, that one produced by the ECM pulling down an output voltage supplied by the pump. More on how those circuits work in this thread.