Coolant Storage Tank Pump

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Collie, Dec 25, 2025 at 4:43 AM.

  1. Collie

    Collie Junior Member

    Joined:
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    Vehicle:
    2009 Prius
    Model:
    Base
    Issue: Coolant Heat Storage Tank Pump was making terrible noises. Heater worked fine but car was giving OBDII Code: P2601 Coolant Pump "A" Control Circuit Performance/Stuck Off.

    No coolant leaks.

    Attempts: Installed 2 separate heat tank storage pumps, 2 separate times (hoping the first pump was just defective). Previously, I changed both of the other 2 system pumps in the last 2 months as well. This being the last pump left to replace.

    Result: Code has disappeared and does not return but the Prius seems to just cook the coolant and not perform a bleeding cycle in Maitenance mode or otherwise just running it, after installing new heat storage tank pump.

    The hose running to the pump gets very warm but the pump it's self is cool to the touch and makes no audible noises as to demonstrate it's pumping anything

    In attempting to bleed it (both valves open running tubes back into where you feed the coolant, the car doesn't want to take in coolant but a little gulp every 15 minutes after it's so hot it's steaming. No fluid comes out of the tube in the bleeder port being opened (the one closest to the battery that you stick a #6 key down into to turn and open)

    Which fuse would I want to check? Getting conflicting info online, the backside of the box cover is no help and doesn't say which one it is. No, I don't have a repair manual lol
     
    #1 Collie, Dec 25, 2025 at 4:43 AM
    Last edited: Dec 25, 2025 at 5:08 AM
  2. pasadena_commut

    pasadena_commut Senior Member

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    Vehicle:
    2007 Prius
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    Look in the stickies in one of these forums, there is a link to a repair manual.

    What is the history of this vehicle? Is there any chance somebody poured stop leak in the ICE circuit?

    Since the pump isn't making any noise when installed I would try unplugging it and applying 12V directly to it (just for a couple of seconds). If it doesn't spin, then it is a bad pump. You aren't installing no name Chinese pumps, right? That stuff is crap. If the pump does spin then hook a voltmeter to those wires and jump the relay socket which would run that pump. And so forth until everything has been verified, including that the tank itself and the hoses to it are not blocked.

    Watch these if you have not already done so:


     
    #2 pasadena_commut, Dec 25, 2025 at 2:14 PM
  3. Collie

    Collie Junior Member

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    Vehicle:
    2009 Prius
    Model:
    Base
    Thank you! Do you have any info on how to apply the voltage to the pump for testing? Merry Christmas!
     
    #3 Collie, Dec 25, 2025 at 3:17 PM
  4. pasadena_commut

    pasadena_commut Senior Member

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    2007 Prius
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    If there is just one pin then it is grounded through the case/mounting bolt, just put 12V on that one pin.

    If there are two pins one will be 12V on one and ground on the other. It may be marked on the pump or connector (ha ha, who am I kidding, it won't be marked.) Turn the car off, unplug the connector to the pump. Take the voltmeter and put it on "Ohms" or "Resistance". Since the car is off one of those lines should be routed to ground and the other, the one that goes to 12V, should be floating, since the relay will not be energized. To be perfectly safe (in case one or more relays are stuck shut) pull the relay shown in the video linked above. Now that 12V line is definitely not energized. Measure resistance from each pin on the CABLE to a clean (unpainted) bolt head. One pin will measure close to zero Ohms, the other will either say something like "OL" or it may fluctuate with a very high value. The one reading zero Ohms is the ground, the other is 12V. Map the cable pins to the pins on the pump (the connector will only go on in one direction). Apply 12V to the appropriate pin and ground to the other, being careful not to short those wires together. There are special probes for this sort of thing that fit nicely on the pins, but one can get buy with insulated wires that have an alligator clip on one end and just a bare solid metal lead on the other.

    Whichever way you do it, one or two seconds should be enough to tell if the motor spins.
     
    #4 pasadena_commut, Dec 25, 2025 at 5:16 PM
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