Hybrid, Power and Transmission computer replacement.

You could buy these ECUs from a car wrecker for a lot less. No guarantee that the ECU's are causing your problem.

 

I suggest that you ask what DTC (diagnostic trouble codes) were logged which led to the diagnosis. If no codes were logged after the first failure, that implies that the 12V bus voltage sagged down, possibly due to the inverter overheating and the DC/DC converter shutting down. With loss of voltage, the ECUs lost their memory of any stored DTC.

Do you know whether the inverter coolant pump is operational? Look for fluid turbulence in the inverter coolant reservoir when the car is either IG-ON or READY.

Does the tech wants to replace three ECUs or just one? Three of the ECUs in the Prius are named hybrid vehicle, power source control, and transmission control.

If in fact it is necessary to replace an ECU, one alternative would be to purchase a used part from a salvage yard. Further, it should not cost $1.4K to replace an ECU so you might inquire further into the quote.

Certainly with a repair quote of $3K you would do well to tow the vehicle to another Toyota dealer to seek a second opinion. Good luck.

 

Are you still on the original 12 volt? If so, it's toast, it needs to be replaced.

However, this may not solve your problem but might aid in actually getting DTCs.

What state are you in? If you're in CA or a CARB state, some of the items they want to replace might be covered by the hybrid system or emissions warranty.

What do you mean by "I have monitored the battery charging system and that seems fine" ?

 

braveheartla,

You did not tell us if your inverter coolant pump is working yet. That could be your "heat related" failure cause and don't continue to run it if that is the case or you'll fry your $4,000+ inverter. Start your car like normal & be sure the parking foot brake is set (so there is no forward lurch to scare you if the engine restarts when you're in front of the car). Take the cap off the inverter coolant fill spout (just to the left of the big square silver inverter on the driver's side---it's safe to do so while it's running, unlike removing the radiator cap). Look down into the filler neck to see if you see any movement of the coolant.

If there is none, your inverter coolant pump has failed, but don't panic. There is a Limited Service Campaign to replace the inverter coolant pump (along with one gallon of coolant & free labor) from the 2004 model through part of the 2007 production (that is in effect through November 30, 2013) all at no cost to you. They will even reimburse you if you already had it dome by a dealer or yourself (if you still have the receipts for the pump & the coolant you may have bought).

Ken (in Bolton,Ct)

 

^^^
LSC A0N - HV (Inverter) Water Pump; Dealer Letter and Technical Instructions | PriusChat

 

I agree w/ everyone else. Seems heat related which could be electronics (ECU's) or the inverter. I would not replace 3 ECU's. The chances of 3 ECU's going bad at once is minimal. I would do everything I could to narrow down the problem.

Here are some thoughts on how to proceed (what I would do (an unqualified DIY hobbyist)):

1) Turn the car to IG ON and check for flow/turbulence in the inverter coolant reservoir. If you have flow, Drive the car to failure and leave it on. Once in failure mode check the voltage at the 12V battery (should be approx 13.3-13.9). If that's good, I would lean more toward ECU's but not all 3. It might be worth your time to simply try to "reseat" the ECU's but I would put the chances of that fixing your problem very low (<1%).

Unfortunately, I don't have any good suggestions on how to figure out which ECU is causing your problem.

 

What exactly is safe mode? I have only seen safe mode on PCs. Was the ICE still running? Look at the MFD when it happens to see if the ICE or electric motor or both is driving or not when this happens whilst fully pushing down on the gas pedal. This may give you a clue.

 

(I registered just to post in this old thread so anyone searching the internet for this problem can find a solution. There doesn't seem to be anything like this anywhere else.)

tl;dr - try changing the aux 12v battery. Worked for me.

I had a similar problem this week. My '06 Prius turned on to the dashboard of death, with all the warning lights on and the screen telling me to park on a flat surface due to an issue with the transmission. After a while, I was able to restart it and get it running normally. This happened three times in two days.

I took it to my mechanic, whose diagnostic tool showed a code relating to the transmission ECU. So, I took it to the nearest Toyota dealership. Their lead mechanic, with 23 years of experience, had never seen anything like this in his life. He went through all sorts of flowcharts they had, which led him nowhere. They called Toyota corporate and went through a flowchart they had, with the end result being a suggested solution of replacing three ECUs, or replacing the 12v aux battery.

The cost for replacing the battery including labor was about $300. The estimated cost for replacing all three ECUs was $3k-$4k. Like other users said above, it's highly unlikely that three ECUs would fail at once. In the end, just like user cwerdna suggested above, I went with the cheaper possible solution of replacing the battery, which seems to have solved the problem!

I hope anybody else who has this ultra-rare problem finds this thread and this solution helps them.

 

Thanks for the post. There was a very similar one not long ago, that included the actual trouble code that was reported by the transmission control ECU. The codes that ECU can report include one for low voltage in the power supply, which was exactly the code they were seeing. That made it a pretty easy call to suspect the battery.

For anyone drawing a moral from the story, a good one might be "pull the codes, they'll tell you useful stuff" (and also, when posting what solved a problem, including the codes in the post will help others later who need to decide if their problem is the same one). Checking your codes can help confirm that somebody else's solution is likely to work for you, if the codes are the same, or point you in a more fruitful direction if they're not.

-Chap

 

I own PRIUSTEC an HEV/EV repair shop in Houston Texas. SYMPTOM No trouble codes!!! And you won’t find this on YouTube either !!! We professional are too busy to post things on YouTube luckily we are here to help you all out. car turns on with one push when pressing the brake but will not ready. Without pressing brake require the usual two push. Will not shift out of park. No response from shifter while pressing brake either. Brake lights ok and brake pedal switch on as well as brake ECU aka brake relay. (There is no relay in that little box it’s an electronic circuit). Brake pedal is Hall effect sensor type so it’s less like to fail.
CULPRIT - Transmission Control Module Software problem. It’s not responding to the Power Management Computer when you press the brake.
Everytime you press the Brake the 12 from the brake pedal switch goes to pin 23 blue wire of the 2nd connector from the bottom which is “A22” if I am not mistaken. The Power Management computer then responds by generating a digital data from Pin 24 also blue wire of the Transmission Control Module. When the TCM senses the brake is being applied it will allow car to turn Ready. The TCM is an important part of making sure the car does not Ready up in gear. This is a dedicated communication between the power management module and TCM and the communication line is mot shared that’s why discrepancy between these two module is not detected by the gateway communication.
SOLUTIONS

 

SOLUTION
Best to replace with a new TCM and have dealer program it. Some shops can program it but very few have the capability. My shop only have the Autel Scanner so I am taking the car to another shop to program the new TCM when it arrives.

 

As with many things, people can have similar symptoms that turn out to have different causes, and of course it turns out that what will fix a problem depends on what caused it.

So, anybody with an issue is well advised to get the trouble codes, as mentioned in #11. When there don't seem to be any, it's important to know the difference between a no trouble codes situation and a "no trouble codes" situation.

Most of the ones we see around here are "no trouble codes" situations, because somebody is using a scan tool that isn't able to show the trouble codes from the ECU that has them, and the best thing to do in that situation is go find a better scan tool and read the trouble codes. We have a thread that reviews a bunch of tools on the market and mentions which ones are good for getting all the trouble codes in the car:

Gen2 OBD2 app review | PriusChat