Prius P261B Electric water pump control

Bill Owner/Technician Michigan Posted   Latest  
Resolved
Driveability
Electrical
2010 Toyota Prius 1.8L (2ZR-FXE) (P410) — JTDKN3DUXA0218067
P261B — Coolant Pump "B" Control Circuit Performance/Stuck Off

Fault P261B for engine coolant pump sets shorty after gas engine starts. Customer states water pump was replaced recently (we are unsure of brand or who did it but it appears to look replaced). I have verified B+ and ground at the pump and can light a bulb on these wires as well. I have 12V on the green wire KOEO (normal). I have scoped the blue wire at pin #10 engine controller (communication signal back to ECU) and have what I consider a normal signal / 0-5 volt square wave when commanding pump on with bidirectional test.

There is a applicable TSB for this fault TS-B-0143-10 but the bulletin only suggests verifying voltage and ground to the pump and replacing the pump…. Being that I appear to have a normal signal when commanding pump on I am a bit nervous about calling to replace the pump

Do I have a faulty ECU or is there something I may be missing here?

Thank You for your time and input!!

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Erik Diagnostician
Florida
Erik
 

You got control. The ECU is commanding it 2550 rpm and it wants to see that. The actual is 0. Powers and grounds? These things fail from 30K to 120K. Check the underside and it might even be melted. You can also bi direction or command it to high rpm and you can hear the motor buzz, whine, or slosh like it wants to and then nothing. Replace. Easy. Tell your customer OEM is best with Super Long…

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John Mobile Technician
Illinois
John Resolution
 

Hi Bill, I have seen this issue numerous times with both Prius and Camry HV. Typically, the water pump is faulty. It may run, but it can't produce the rpm signal. The reason for the code is that there is no feedback rpm to the PCM. Going from memory, the PCM puts 12 volts on the rpm feedback wire and then the water pump electronics toggles it low. You could toggle it low with a testlight and…

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Ahmad Engineer
Jordan
Ahmad
 

Replace the water pump.

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Matt Technician
Massachusetts
Matt
 

Hi Bill, I would make sure the replacement pump is a OE Toyota or Aisin ( Aisin is the OE manufacture and will have “Toyota” grinded off the aluminum casting, you can see this with a mirror) I would be worried about a non-OE pump. Here's a couple scope captures of a brand new Aisin pump. Hope this helps.

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Bill Owner/Technician
Michigan
Bill
 

Matt -thank you very much for the scope pattern! I can now see my signal on the green wire is incorrect .

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Mohammad Owner/Technician
Illinois
Mohammad
   

As Matt Lamontagne suggested, replace the pump with an OE one. This pump runs all the time when the the system is “Ready”. Aftermarkets with ⅓ of the price of an OE are tempting but would not last. Just a thought.

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Matt Technician
Massachusetts
Matt
 

Happy to help! I'd love to use this as a case study for training. Shoot me an email at … I'm interested in more info on the faulty part

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JB Owner/Technician
Minnesota
JB
 

This scenario is reminiscent of what happens when an aftermarket fan controller is used on a VW or Audi. The inferior quality electronics found in many aftermarket products are unable to recognize either the command signal (fan controllers on Vw/Audi) or unable to provide the required feedback/verification signal to the control unit (what it sounds like is happening here). If wiring between the…

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Eric Owner/Technician
Michigan
Eric
 

Every one of the Gen 3's that set this code need a pump. Actual and desires rpm should be very close, obviously yours aren't. The Toyota TSB calls for replacing pump, not sure what upgrades they made to pump, but OE only on these.

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