Testing Gen 3 Water Pump

I think you spent way more money than a mechanic would have charged if power to the pump was the real issue. The ecu could be bad as we discussed earlier. But it sounds like electrical troubleshooting is not your strong point.

One issue is your check engine light will stay on, meaning you may not know when another problem comes up. Thermal cycling of the engine is a big issue as well, maintaining an even cylinder temp is important to an aluminum engine. Thermal cycling is already one of the weak spots of a gen3 engine. Some think it is a root cause of head gasket issues. Gen4 has significant improvements in this area. I did a video showing the dramatic temperature changes possible because of the engine stop starts, now you have a separate control for the water pump. Getting it fixed right would be a good plan.

 

And like I said it’s great way to avoid having to pay a $500 towing bill to a shop. And if they fix I can just sell the controller. So it looks like a win for me even though electrical troubleshooting isn’t currently my strong point but common sense is . I got the job DONE.

 

I'm definitely late to the conversation but have been having the same issues on my 2013 Prius V. it keeps throwing up the P261b code and going into emergency mode. I have replaced the water pump 3 times with the factory OEM pump (asian sp?). i have ohm'd all the connecting wires from the relay/fuse and also from the ECU-- everything as turned up fine, no loose connections or other issues.

I've noticed the old pumps i removed will run with 12v,
I tested the relay, it clicks.

I figured I would just throw parts at it.
I got a rebuilt ECU from FlagshipOne coming.
after reading through the posts, I might get a new relay. and might try to look at the connectors on the Relay harness, (apparently they can get contaminated).

I'm trying to give as much info as i have, and i will update if the new ECU solves my problems.

I hate throwing parts at a problem, but I also hate getting the car towed and/or head replaced.

If anyone has any thoughts or recommendations that haven't already been brought up, let me know thanks.

 

If you're looking at a P261B code, here is a post that explains what that code means and has ideas on collecting the information needed to troubleshoot it. In that post is also a link to an earlier post where those suggestions were more detailed (and that earlier post referred back to earlier ones in the same thread that might help too).

Since the code means the pump seems to be doing less than 900 RPM when the ECM wants it to run faster than that, most people start off by checking the easy reasons why the pump might not be running at all (which definitely counts as less than 900 RPM).

The tricky situations are where you've already done a couple simple rounds of "what if I just try this and see what happens?", but you're still looking at the same code.

If you find yourself in that situation, the smart money might just say "ok, no more foolin' around", and escalate directly to begging or borrowing an oscilloscope and finding out what those pump control and feedback signals are really doing. Spending much time trying to be clever with less might only prolong the agony.

There are more details on how the pump is controlled in this post and following. There you'll see what an oscilloscope ought to be showing you and how to interpret it.

 

Hey did the new ecu from flagship fix the problem ?

 

Any update on this? Is the problem fixed?

 

I'm not sure if i should worry about it. I'm afraid, it's a unicorn case