ECM fried by coolant control valve repair?

When the replaced the coolant valve, most likely they didn't replace all the coolant that was removed. If the mechanic is not familiar with the Prius, there's a chance they didn't get the air out and fill the car with coolant. Your car overheated from the lack of (low) coolant. Nothing else.

 

You took the words right out of my mouth JC91006. Purging all of the air can be very tricky and time consuming and is imperative that it be done completely and correctly! They should be held accountable in my opinion as well OP!

Posted via the PriusChat mobile app.

 

There are three wires connected directly between the water valve (coolant flow control valve) and the WSL1, WSL2, and WBAD terminals of the ECM. These are shown in Electrical Wiring Diagram (available by subscription to techinfo.toyota.com, and to the dealer on Toyota TIS) in the Engine Control part of the System Circuit section:

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While troubleshooting and replacing the water valve, if a technician caused any of these lines or circuits to be exposed to voltages or currents in excess of those for which it was designed, or if there was an electrostatic discharge, the ECM could have been damaged. Without the ECM design and test specifications, which Toyota doesn’t publish, it’s hard to assess the likelihood of this, but it is possible.

It’s usual in the design of electronic control units for automotive applications to include protection from such abuse, but that may not have been done here, or the protection may have been insufficient. In the Repair Manual, Toyota indirectly acknowledges this possibility, with the warning, “Before performing electronic work, disconnect the cable from the negative (-) battery terminal to prevent component and wire damage caused by accidental short circuits.” (This is in the Precaution section of the Introduction, by the way.)

If the dealer won’t absorb the whole cost, perhaps you could offer to pay for the new ECM, discounted to their cost (not the usual retail price), if they agree to pay for the labor.

 

OP just has to ask the service manager if the ding dong tech followed the Toyota Service Manual procedures?
Have the manager/tech tell you what the procedures are.
If he/she doesn't state disconnect NEGATIVE battery cable, Toyota repair procedures were NOT followed.
This can be corroborated by the original return of the vehicle with the correct time and radio presets maintained, assumed.

The 12V memory savers that plug into the cigarette socket, will not work for the Prius b/c of how the cigarette socket is wired. Furthermore, this article says industry experts (collision repair people) do NOT recommend use of such devices.
Memory savers not recommended by industry experts | Search Autoparts

Good Luck. Hope they cave in.

 

I think what happened to that ECU might be a coincidence. I don't just see how what they replaced, could ha e caused the problem. The coolant valve has connectors I think on it. Replacing the valve does not have to involved wire splicing, or so. So, there should be no way a short could have occurred that fried the ECU.
My thought is that there may have being another thing that caused it.

 

To the OP. If you want to get to the root of the problem, and of you are a DIYer, you could try taking a look through the coolant valve harness wires, and see of there had been any signs of splicing the wires, or coolants contacts(I doubt that would cause the ECU to burn out).