Gen 3 to 4 engine swap failure

P261b

 

I checked all the wiring again and again it looks good. I unraveled it pretty much and found nothing. I checked voltages on the pump harness. Pos 0volts. Thin green wire 14.4volts, thin blue wire .03 volts. I tried jumping the pos and and it powered up the pump So at least I know the motor works. But it does really look like it’s an ECM problem and I’m kind of wondering if it’s the engine swap causing some kind of incompatibility with the ECM? I have no clue I think I’m just going to try a standalone water pump control unit so that way I could at least maybe drive it to the shop and they can look at it and tell me something new. Oh and I did a run techstream on it and I tried reprogramming the ECUs , health check and active test to run the pump but it would not run it and just came with the same code P261b. I’m thinking possibly an update for the ecm could be a solution ??

 

It came with a 4 gen water pump and that would not work either but the motor will turn if you apply 12volts.

 

What year is your Prius? I’m wondering if different models have other types of ecu’s. Currently I’m still having a water pump problem. I bought the one the senior members here recommended which had good reviews all around but still the same. I checked wiring and it seemed good but the voltage readings seemed weird. First no power to the POS. NEG is good. 2 sensor wires blue .03v , then green 14.5v. I think the green wire is normal for voltage coming from dc/dc inverter but the tach wire is almost grounding out before the ecu can send the correct voltage to the pump motor. I’m wondering if there’s a grounding issue I missed but I’m not seeing it. I heard the fans kick on and swapped the relays but still nothing. How can the current not get signaled to the pump? If everything else is working then the main ground must be good. . IDK. MYSTERY

 

Yeah the only reason I think that is because I read an article here Someone did a gen 3 engine swap and had similar issues and the dealer reprogram the computer and it worked, Also when I use techstream reprogram nothing seem to change the check engine light stay on my dash everything Stays the same stays so maybe the v16 I downloaded isnt working right I’m not sure it’s hard to say so many variables pop up and lead you down so many different avenues. Also I’m pressed for time I use my car for work and I have tried everything I can think of and having conversations with some people on this forum are like pulling teeth. You seem very helpful here and I appreciate your responses thank you. I want to look into the wiring I’m thinking that if there is an issue then it’s somewhere in the main fuse box somehow with its grounding and current is going to the relays I took the relays off and checked them both had the same amount of ohms resistance I think I am not really sure how to check that out somebody was talking to me about different pins . If I could find a picture diagram someplace where I could just stick my tester you know here and there and see what comes up that would be probably the best route for me. I actually have two cars gen 2 & 3. I realize that if I get my gen 2 up and running I will have a second car in case Gen 3 goes down again instead of driving my gas guzzling dodgeRam truck.