Coolant pump B control malfunction (P261B)

Has nothing you've read in either of your threads about it in the last 3 days seemed to shed any light on that?

 

In 3 days so far, I cleaned the heater core, tested water pump relay ,water pump plug voltage. All good.
went to a mechanic to read / test wp but his software won't read or test. My techstream crashes when I tried to test wp.

 

Ok, it's good that you've done some of those things. How did you test the WP plug voltage exactly and what were the results?

The "mechanic's software won't read or test" and "my techstream crashes" are obstacles for sure; it would be easier if one of those could be overcome.

 

found a bulletin, D13-2 (NWP) - Body ground 11-14v, D13-1 (+B) - Body ground 11-14v.

I got 12 v on both. So plug is good.

 

That's a useful step. I assume you mean you had D13 disconnected from the pump and these measurements were with ignition on and the engine not running. That NWP to WPI circuit is the one that brings the pump speed back to the ECM, which is what P261B is about.

The easiest way I've found to probe it while the pump is operating is where both those circuits pass through the underhood fuse box, as described in this post.



Top trace is what the WPO - SWP circuit should show, bottom trace the NWP - WPI circuit, when the ECM is requesting about 40% pump speed.

 

Yes I did read your thread. I guess I don't have a tool to check that square waves.

I am thinking of checking w/p again. Open and check the propeller.

 

BTW, maintenance light is on. Tried TripA,Km + double On, but won't work. Mechanic software won't connect. I am thinking if ECU has issues?

 

Sometimes there can be things that just have to be seen to get to the bottom of a problem. With your Techstream crashing, your mechanic's software not working, and no oscilloscope, you've got drastically restricted visibility into what's going on. Progress on any one of those fronts could make it easier.

Generally oscilloscopes aren't cheap enough to be casual purchases yet (unless there's, like, a university salvage outlet nearby), but an automotive shop or an electronically-inclined buddy might already have one. Also, for the signals involved here, definitely nothing fancy in the oscilloscope department is needed. We're talking tens of Hertz, not megahertz or gigahertz.

 

I missed to mention my other observation other day.
At >55 mph in hwy, I got beep noise with "Hybrid system warning" symbol in display. But I pulled error code with my Torque android app that gave me P261B.

At that point I reset error code from app and came home slowly 40mph< to home.

 

One reason not to drag things out too long when there is a reported water pump code is that even if you are watching the coolant temperature carefully, that's the temperature where the sensor is, and if the coolant isn't being circulated effectively, it can be other temperatures other places; sometimes that even includes localized boiling spots, which separate the coolant from the metal to be cooled. Repeated enough, that can take a toll on the engine.

 

I've always heard that it's best to replace the water pump with the thermostat when you have a problem with either one. They are right next to each other and usually, the thermostat isn't that much more work and doesn't cost much more. So why not change them both so you won't have to in the future, potentially?

I found this thread by googling "Engine Coolant Pump 'B' Control Malfunction" which I am also getting on my 2016 Lexus ES 300h with 279k miles. I'm an Uber/Lyft driver and so I'm doing everything I can to learn about how I can fix this issue myself without paying a mechanic an enormous amount of money that I don't have.

Found an $80 pump on Amazon (Gotta Love Amazon!), yes it's generic but I need something right away and don't have $400 to buy an OEM one from a reliable source at the moment.

I too am concerned about the "B" in the code given. I mean if there is a "B" then there must the an "A" too, right? What is "A"? Is that the petrol coolant pump? Because if it is, why does it seem like my petrol water pump is out but a code of P261B is being triggered when P261B sounds like the inverter pump? And BTW, my inverter pump is a little noisy but it's always running while the car is on.

I will be attempting changing this petrol water pump and hopefully the thermostat (if I can find one) on Saturday. I hope for the best!

For anyone who has a 2AR-FXE (Hybrid) engine, this video should help you tremendously in seeing just how easy it is to change this on a 2AR-FXE engine...