Mayday, Mayday, Mayday P3120 error code!!!

Welcome aboard.

Sorry to read your troubles.

First, what kind of reader/scanner are you using? Is it Prius specific or generic OBD2 reader.

The reason I ask there may be other codes your are not seeing.

Jim

 

Yep, she's a peach alright.

I have no idea, but my guess is that your problems manifest from having a 15 year old Prius with over 240,000 miles on it.
Good Luck.
If you have the skills I have no doubt you'll keep her on the road.

 

Confirm health of 12V with a load test. Replace if bad.
Get MiniVCI for diagnostics.

 

I'm at work so I don't have my manuals handy. But next best is the Yahoo Group, "Prius Technical Stuff":

Yahoo! Groups

I followed the quick start guide to plug it into the Prius,
connected the battery, communication started and (as expected) no
codes were found due to the absence of battery. Then I started the
car, let it do its clunk-----clunk and restarted the tester.
It found one code:
P3120 HV Transaxle Assy
Well, it was expected that it would report something like that
but I could not find any sub-codes to get more detail.
The "enhanced" Toyota display of the tester reported that no
enhanced codes were found so this is all the info I have.
I will probably need to wait to get more info until we have time to
swap engine and then disect the old engine - unless someone wants to
buy it, then we can just peer through the plug holes if something
obvious has happened...
I do plan to sell the transaxle and inverter unless I can find a
better use for it myself...​

We really need miniVCI metrics but I'm OK if you want to get a full readout from the Toyota service center. But a couple of questions:

• Do you hear a hum/rumble whose frequency varies by the speed?
• If you shift into "N" (turns off the power electronics), does the rumble remain?
• Can you make a video/audio recording with the speed?

I am most interested in three temperatures:

1. ICE coolant temperature
2. MG1 temperature
3. MG2 temeprature

In a healthy Prius, the ratios are:

• ICE > MG1 > MG2

In an unhealthly Prius transaxle:

• MG2> MG1 and ICE

I need to explain that MG2 is on the end of the engine-transaxle stack and though it has a coolant channel, the bulk of its cooling is ambient air (and there is a LOT!) When there is a stator short, it becomes a default generator coupled to the spinning rotor of MG2. It generates power that the short converts to heat. It is the spinning rotor that causes the heating. This exceeds the cooling capacity and there in lies the problem.

One risk is the DC-to-DC converter is on the bottom of the power inverter and sits on top of MG2. It can easily be overheated leading to a 12V voltage supply problem and dead 12V battery.

Bob Wilson

 

Wow, Dr Bob, that is some reply with one hand tied behind your back :-D

OP, I suggest getting or borrowing a PRIUS aware scanner. Preferably the Mini VCI $20-60 on ebay or amazon, It includes the Toyota diagnostic program that will also read PRIUS underlying codes.

My Generic OBD2 gave me a reading of P1636, but it was false,well sort of but it was misleading, Code does not exist in Toyota. Purchased the $22 Mini VCI, it showed P3006, P3000 but not P1636.

Without the real error codes, you are flying blind.

 

For $79, insist on getting the print out. It should have all the readings you need. If they won't, ask to see the readout on their screen and take a pic

Yes, some are experiencing trouble with the loading of the TIS Mini VCI driver to make it a standalone version. But it comes down to operator error in loading the program and/or using the wrong Operating System on their laptop.

All or most MiniVCI's use 32 bit Windows XP or less version. The one on Ebay for $60 uses Windows 8.0+ and either 32 or 64 bit. The trick is not to open the TIS until the "standalone" Mini VCI driver program is copied and pasted in the the TIS program. Your PC may ask if you want to copy an older version of the program, answer is YES, this will make it a standalone.

 

Did you check the inverter coolant tank to make sure the inverter pump is running?

With the car on, the fluid level should appear split with visible motion if you take off the fill cap.

Bob Wilson

 

^^^+1

 

C1259 is just a code from the brake computer saying "hey, go talk to the HV computer, it's got something to tell ya."

P3120 inf 241 for a sliding torque limiter, plus a funny burnt smell, makes a perfectly consistent picture. That's the part that looks just like a manual tranny clutch but has no pedal to release it. The parts are shown here:

31270 and 31290 but as you can see there are various suffix numbers available, and this particular dealer diagram seems to have both parts listed under both numbers, something got mixed up. Anyway, looks like $300 to $600ish in parts depending on which prices are right. The daunting part is the labor.

-Chap