P261b OBD code. Coolant pump problem

When was the last time that your coolant was drained and refilled? When my dealer did that job, they failed to completely eliminate all the air in the system. Driving my 2004 Prius a while cleared out the air and left me with a low coolant level.

JeffD

 

It was due at 100k miles and again every 50k miles thereafter.

JeffD

 

Is this post about the 2016 shown in your profile?

 

What's the consensus on the water pump here: preemptively replace every 100K miles? Or not soon thereafter? Thermostat too? @Raytheeagle ?


Too many questions, lol.

 

Or the coolant??

 

Confirmation is good. You'd be surprised how many posts are from people having more than one car and neglecting to specify which. 242k is a pile of miles for a 2016.

 

Change the pump out it is already going bad.

Posted via the PriusChat mobile app.

 

My calendar/mileage date for the coolant would have been last year, but I had a bunch going on at the time so I dipped a test strip in and it came out fine so I spent the time on other things. When the weather warms up again I suppose I'll dip another strip, or just go ahead and change it.

The pumps do seem to have an awkward failure mode possible, where the impeller comes apart and then the pump rotates easily without moving coolant. In 2010 there was a trouble code for pump RPM too low (that's what P261B is), but none for RPM too high, which is what happens when the impeller is busted. So in a 2010 you could have your pump thoroughly busted, not cooling your engine, and get no trouble code to tell you that.

Apparently a code for RPM too high was added in 2011 (P148F). I would (nice person)-u-me that a 2016 has both codes, but it would be better to check the manual.

What puzzles me in this thread is how a low-coolant situation could have led to a P261B, as the first post suggests. I would expect, if anything, a P148F if there was such low coolant the pump was slugging air.

I have one nutty speculation that I have not yet had any time to test. In another post where the impeller busted, the Techstream-reported pump RPM was somewhere in the low 6,000s (I think full speed is normally 3,000-something when the pump is really pumping). It was a 2010, so no P148F code, so no trouble code at all logged, at least for low-6,000 RPMs.

The possibility I'm wondering about (again, I've not tested this at all) is whether the ECM's pump-RPM scaling allows the RPM to wrap back to "zero" above some maximum RPM, such as, let's just guess, 6,553.5. That might allow, in some cases, an over-revving pump to set the under-revving trouble code.

Still, in any car that has the tailor-made-for-over-revving P148F code, I would expect that one to show up first....

 

Low coolant and 242k miles: ever cleaned the Exhaust Gas Recirculation and Intake Manifold?

 

So once you get that code P261B
It is time to change it out, trust me.

The reason for low coolant is because it is turning to vapor in pockets because the pump is not circulating the coolant as it should.

Hence low coolant and you will still get the code again.

You will not like the outcome of total shut down when it completely fails.

Posted via the PriusChat mobile app.

 

That's generally my philosophy too, but at 240,000 miles some maintenance if you want the vehicle to last much longer is in order, especially since replacing the coolant pump is not that difficult or expensive.