'02 with 489,000 code p03120

I pat myself on the back for realizing a decade ago that the inverter is the achilles heel of the Prius, not the battery etc. A billion kudos to Toyota for building one that lasts ~500k miles.

 

With ~500 K miles, everything on the car is either worn out or very worn. I've tried keeping super high mileage vehicles going and all of mine turned into money pits. It was an amazing run, but it's time to pay last respects and move on to something with a mere 100 K to 150 K miles. Sounds like this owner could get 600K out of a Gen II.

 

Simply, bloody effin' incredible. WOW. :cheer2:

 

After you remove the old transaxle, do you plan to disassemble it? I know that the group would be very interested in photos that show why the transaxle failed.

 

489 k miles = 792k km

Bob Wilson

 

Toyota has established regional quality offices. If you Google for "toyota quality office" you'll get a number of hits on "Product Quality Field Office." You might be able to find a phone number and give them a call. However, I suspect if Toyota is interested, they will want the whole car for disassembly and testing. It may make more sense to see if the owner is interested in contacting Toyota knowing they may want to buy the vehicle.

On the transaxle:

1. drain oil and take a sample in a clean bottle - this gives the option of oil testing.
2. drop the transmission pan and photo and inspect the debris

This is similar to what some salvage rebuilders go through. The biggest risks are a wire or connector being damaged. One rebuilder turned me on to Auto Enginuity, a poorly supported but extensive scanner. Auto Enginuity does not report inverter subcodes but we were able to help on related symptoms and supporting data from Auto Enginuity.

Toyota has a TechStream Lite that at $1,200-1,500 might provide more detailed and accurate data than Auto Enginuity. I would certainly expect it to be supported and current. Auto Enginuity has bugs but their support is not very good (they ignored reports of false data values and claimed the 'spike' of false codes was due to real errors and dismissed Firestone reports of no brake codes.)

The other risks associated with our NHW11s:

• accerator encoder - a dual-pot with mechanical wipers, I just sent another rebuild out for another 2001 Prius. It seems to be more common with the 2001 and some 2002 Prius. The Toyota replacement is ~$500.
• steering torque sensors - another failure that acts like noise in the sensors but replacement is over $1,000.

I would recommend doing a survey of 2006 and later, used Prius. The 2004-05 Prius had a problem with weak solder joins in the MFD that good Prius friend Hobbit had diagnosed and shown how with careful soldering, could be repaired. That is the only common weakness I'm aware of in that model and there are at least two credible, salvage rebuilders, AutoBeyYours and Re-InVolt. Many weaknesses of the NHW11 (2001-03) model were designed out of existence with the (2004-09) models. Best of all, the NHW20 is getting about +2 MPG over the NHW11.

The NHW11 has many nice features but in the used market, the difference with the NHW20 may be vanishingly small. I would recommend looking at completed, Ebay sales. Given the last model year of a series, 2003 for NHW11 and 2009 for NHW20, the data suggests these are the most worry free as they pickup the accumulated manufacturing fixes.

Bob Wilson

 

Was that the one you mentioned earlier?

The thermistors work by high resistance in cold and low resistance in heat. It sounds like the MG2 sensor wire is open.

If you can put say a 200-500 ohm resistor on the sensor wire, you should see a more normal temperature. But right now it sounds like an open circuit.

Bob Wilson

 

What was the temperature of MG2 in the freeze frame for the original code?

Yes. It is not separately replaceable. Are you sure the sensor connector is plugged in?

 

I was thinking of this:

This may help:
Prius Hybrid Vehicle ECU

For MG2, the signals are MMTG and MMT:


We had a thread a while back with user 'tomfreed' who was swapping transaxles:
http://priuschat.com/forums/generation-1-prius-discussion/71110-problem-car-5.html#post988886

One of his problems was traced to a temperature sensor.

Would you be interested in trying a Scangauge II to try and read out the subcodes? User 'vincent1449p' has proposed some XGAUGE setups that might read out the subcodes from the HV ECU. If so, this could provide a direct path to diagnosis of the remaining problems. But I don't have a transaxle problem that requires reading out these codes. If interested, send me a PM with mailing address and we can work something out.

Bob Wilson

 

Those are the HV ECU terminals for the circuit. He's looking for circuit and sensor location.

Although the sensor itself cannot be directly accessed, there is a connector on the lower front case of the transaxle, towards the driver's side. It is best accessed from below, after removing the undershield next to the drivers' side front wheel well.

There is another sensor connector in the immediate vicinity, which plugs into the end plate of the transaxle. This is not the temperature sensor connector, but the resolver connector. The temperature sensor connector plugs in to the front of the case itself.

He has a professional scanner. If he has the correct software for it, but can't read the subcodes, the issue is not in the scanner.

 

Nice work, finding that wire in the harness. What was your process to determine the wire was open? Were you able to determine a cause for the wire being broken (rodent damage, shipping damage, a prior accident, or ?)

I am wondering whether there was actually anything wrong with the old transaxle? Regarding photos, if you find visual evidence of a failure (like burnt stator windings or worn bearings) that would be very interesting to see.

 

Patrick pretty well identified the primary areas of interest. I would like to add some as you have time. Could you inspect the area around the differential with particular attention to:

1. debris, sludge - photo and save a sample in a clean, plastic bag. This is one area we can't reach when changing the transaxle oil and I've suspected that the sealant debris eventually floats into this area to get 'ground' into a fine, suspended powder.
2. seals - some of the transaxle oil testing showed evidence of external contamination. The likely paths are either the axle seals or the engine seal. Abnormal wear patterns and scuffing might give a clue.
3. engine torque limiter - the old engine has a pressure plate that is bolted to the flywheel. I would be interested if there was evidence of slipage and wear. Of course the engine shaft seal would be interesting to see if there is any evidence of dust or dirt invasion.
4. transaxle vent - on the backside of the transaxle is a one-way valve called a transaxle vent. Due to thermal cycling, this part normally vents hot air and cooling leads to a partial vacuum. The little brass cap can be removed and inspecting the seal and surface would help.

How recent were these changes? Was there something that triggered them?

Did you swap the axles as part of the transaxle-engine swap or reuse the existing one? I have no clue as to which approach is easiest (or less bad.)

I would also be interested in photos of the exhaust manifold from the old engine. The reason is Daryl, a local Prius owner, has a failed, catalytic converter that may have been due to excessive oil and/or engine oil leakage. Alabama does not have annual vehicle inspections so he just drives with the check engine light. Your client may want to pay early attention to engine oil quality and level (fill only to just under F, some recommend 3/4 ths of the way between E and F.)

I've made the assumption that the engine swap did not include the HC converter, the first one after the exhaust manifold. Any lessons learned in this area beyond "lots of penetrating oil and grunt like heck."

You've done a great job and been patient with our questions. Please don't be a stranger but pop back every now and then and share 'lessons learned.' <grins>

Thanks,
Bob Wilson

ps. 4,000 miles Jeep Cherokee, 20 MPG -> 200 gallons! OWCH!!

 

20 mpg is pretty optimistic. 15 mpg is probably a more realistic figure.