2002 prius transmission failure ?

When the gasoline engine is running, MG1 also needs to rotate to allow the gasoline engine to provide power to the drivetrain (or not, depending upon driving conditions). It sounds like this is not happening, and that could be due to a transaxle fault as you suggest. It is also possible that this is due to a hybrid vehicle ECU failure, since that ECU controls the operation of the transaxle MGs.

 

The gas engine, generator (MG1) and motor (MG2) are connected by a planetary gearset. Proper operation depends on having members turning, holding, or freewheeling. Shuddering is a definite indication of a transaxle failure, usually MG2. I see a trans R&R in your future.

 

P3125 is usually the inverter or the transaxle. It depends on the 3 digit INF code and the diagnostic chart. For example, code 287 (?) would have you check MG winding resistance and high resistance (more than 100 mOhm) there would dictate a transaxle replacement.

 

IMO, that is correct. If the battery is charging with the ICE running, it is my belief that the inverter is working. But it is only my opinion. I kept getting a p3125. I would clear it, and when I would start the car the error lights would come on, the ice would shutter then die. I replaced the inverter and all is well.

 

The inverter has separate circuits that drive separate two motor generators:

• MG1 - provides counter torque to engine and generates electrical power. However, sometimes it 'sinks' power in what has been called 'heretical mode.'
• MG2 - provides reverse power and takes the energy from MG1 up to around 25-30 mph. Thereafter, it works as a generator and sends power to MG1 to force the engine to turn slower (aka., 'heretical mode' which is Prius for 'overdrive.')

If the car starts and runs while in "P" with no other codes or problems, then MG1 and the inverter circuit for MG1 are OK.

If you get a code when shifting out of "P" with a major alarm, we begin to suspect MG2 is burnt. If you can drive and there is a rumble that changes with vehicle speed, not engine, vehicle speed, then MG2 is toast. You can pull the transaxle filler plug and sample the oil. If it smells burnt and looks burnt ... time for a new transaxle.

Sad to say, this does not prove or disprove the inverter is bad. A failed MG2 would mask inverter symptoms.

You can get a ScanGauge II ($100-120) in a couple of days and code in the XGAUGES to read out the codes other scanners can not see. I strongly recommend this approach as gross symptoms can often be ambiguous.

Bob Wilson

 

Cool!

You went into the deal with 'eyes open' and I admire that. Swapping the transaxle is bad but not if you have a good floor jack, jack-stands, and an extra pair of hands to help on the awkward parts.

Note, I have seen inverters also fail with a bad transmission but in that case, there was strong evidence people were driving around for hundreds of miles and using batteries to substitute for a failed DC-to-DC converter. Inverter swap is a piece of cake compared to the transaxle.

GOOD LUCK!
Bob Wilson

 

That looks like good news. Have you found a fast, reliable source for the select-fit bearing preload shims (described in the shop manual and also in this Art's Automotive repair write-up? That seemed to be the only reason the repair at Art's dragged out to 40 days. Or will you be using the Jack Rosebro/Luscious Garage in-place stator replacement technique? -Chap

 

I would build more of a jig then just hoping it doesn't crush something. Huge forced involved. At the very least, those thin plastic cutting board sheets that are like 12" by 24", you could make a tube to guide it in... Maybe not enough clearance...