Why Prius ECU can't reduce battery temperature while Dr Prius app can?

When that white plug in the back rear right quarter get corroded the fan certainly does not work as expected and when they're corroded and broken it doesn't come on at all . It forces you back there to fix it jumper it something I now in the four twos here the fans seem to work as expected . I'm in the 100 not blowing batteries . We also not hard on car I other cars to beat on.

 

@amitt are you getting any codes?

Repair Manual excerpt attached:

 

No codes, i was just actively monitoring temps on dr prius on a hot day. I had suspected this fan for a couple of years now, tried to clean twice, and put some oil on the splinder of the motor.

But when i saw the texhstream mode 4/5 attempt with no fan response, i knew that something is wrong with that auto mode PWM.

Tombukt, that symprom will happen only in auto mode , but work fine in manual active test mode or via dr prius?

 

Both screenshots you attached there are showing VMF = 9.4 V for control mode 4. Is that the VMF value you're saying is wrong, or the one you'd consider right?

 

Correct, 9.4v is not a good feedback for speed #4 , how do i know besides trusting my ear that speed #4 was not on?

Well... look at the attched screenshot i took with " active test mode" video, at speed 4, the voltage should be much below 7.4v , ( just toggled through the speeds fast without letting the feedback settle) at speed 6, the voltage goes down to ~ 2.5v

BTW Mendel, thx for the pdf, i found the needed page regarding PWM signal ( attached) it appears that when the signal down time increase, the fan blows faster. This mean that if there is noise there ( signal high) the fan will not blow properly because the duty cycle will be too short, or it will not blow at all.

Now i need to get my old back to open those trims again and probe it. I was involved in a car accident recently and im in really bad pain, i dont see myself doing this before i get better , honestly. I was hoping it will not be a physical fix.

I live in the bay area, if you're a diagnostic freak and feel like you want to help me solve this for the good of this great community, im open for help i got the scope and everything... just no muscle power , and herniated disc

 

Just for fun, to continue the previous message, this is the image of feedback voltage reading i got with speed #6, the feedback is at 2.8v.
This means that as the actual fan speed goes higher, this voltage goes lower.

I wonder why toyota decided to let this go out of control and not monitor whether the fan is not spinning at the correct speed that the ECU order it to go, and instead just rely on the temperature sensor to shoot a fault , only when the battery is very, very hot.

This is definitely a problem with this design, since i doubt that even toyota technicians know how to read this feedback, they would probably just toggle the speeds and determin that everything works properly in active test mode, but its obviously not ok when you switch to auto mode.

Chatgpt claims that in later models, toyota added an encoder to monitor actual fan speeds.

I wonder how many gen 2 prius owners slowly cooked their hv battery until it died this way.

I bet that there is noise on that signal, which interrupts the duty cycle and the "low" time of that PWM signal, which makes it only blow at very low speeds, or not at all, which is exactly my problem.
Why the PWM is not wrong in manual mode? Maybe because the signal that causes noise ( due to corrosion or whatever) is disabled in manual mode.

My problem seems to happen to other prople online that wondered why their fan is not able to cool down their battery.
Some people responded to them that toyota engineers knows what they are doing and this is how it should work even with these high temps, but !, the fact that the ECU iteslf, that toyota engineers designed, orders it to go to speed 4/5 and it does nothing or spin very slow, is a clear problem with this design, and a problem with the lack of processing this feedback voltage, to at the very least, log a warning in the ECU.

That is just too sad, those gen 2 prius are solid otherwise.

Please let me know if you live in the bay area ( im in SJ) and can help me as a prius diagnostics freak... in any case this forum is so fun, i like to talk about problems with my old beloved beater prius, with other knowledgeable people . Much appreciated !