Orange4boy's Rescue and Revival of a 2003 Prius

[orange4boy]

The Honey and I have been keeping our eyes open for a cheap, fun fuel efficient second car to use instead of the Golden Egg for Bowen Island commuting and long highway trips. We looked at the classic Insight, CRX, Metro, Civic etc. but hadn't been able to find something affordable or suitable.

So We were browsing Craigslist the other day and saw a Prius for $2500. The only major problem was it was throwing a dreaded P3120 HV Transaxle failure code. We did a bunch of research and found a couple of people who had done the swap themselves so we decided to buy it.



The listing had started higher and dropped to $1500 by the time we got to see it. It's an ex Co-operative auto network car so we feel like we rescued it from it's servitude.

Now we have to get it home. Luckily one of the benefits of membership in VEVA, The Vancouver Electric Vehicle Association, is use of the VEVA car trailer. So along with Dave, the member who sold me Robotrak, the Remote controlled Elec Trak, we will pick her up later this week.

Then the "fun" starts.

Thanks to bwilson4web for your help!

[Daox]

Nice find. What does that tranny code usually indicate? Bad transmission? So you need swap a new one in?

[orange4boy]

Yeah, according to Bob Wilson, supposedly what happens is somehow windings in MG2 develop a short which leads to overheating of the tranny which leads to a downward spiral. I have the entire sheaf of service records too and I can't find an entry for transaxle fluid change. These are super important from what I have read.

Now I have to find a replacement for MG2 or the whole shebang. I found one on ebay for about $700 but I'm going to keep looking locally first.

I'm wondering if the First and second Gen can be swapped. Anyone know?

There is still and off-chance that it may be under warranty if I can prove that a previous warranty defect may have caused the failure. The records show an inverter pump failure and an ecu which were fixed under warranty so maybe...

[jamesqf]

Have you tried here: http://car-part.com

[orange4boy]

Thanks James.

Found one using car-part with 19000 km in Alberta. $1200. A bit pricey but with mileage that low, could be worth it.

I did find one in Richmond for 1200 also. Will have to see if they will come down a bit. Don't know the mileage.

Also found one on Ebay for $700 with 75000 km. Shipping $120

[bwilson4web]

This is one example of a burnt MG2:



This is one of three failed transaxle I've seen photos. One failed in Germany and was disassembled and the other was documented by Art's Automotive.

Bob Wilson

[orange4boy]

That's some serious copper.

Have they figured out what makes them short out? Electric motors are notoriously robust, their main enemy being heat. In an oil bath I suppose debris might also pose a hazard. Is there a fluid cooler on these? Who winds them? I'm guessing it's Nippon Denso.

I need a new alias... how bout rapidfirequestionboy?

I gather MG2 failure is a pretty rare occurrence.

I found some OEM shop manuals on ebay. I guess I should get the 2003. They seem to be about $130-150 a set.

[jamesqf]

Originally Posted by orange4boy

Found one using car-part with 19000 km in Alberta. $1200. A bit pricey but with mileage that low, could be worth it.

Maybe one of us is doing something wrong? I was seeing a bunch in the $600-700 range... Or were you looking just in Canada?

[orange4boy]

That would be me. I was trying Canada first. I did another search later for Washington where I could drive to pick up and found 12 units between $700-850. Looking good. Just have to pick one and go for a drive. Probably won't happen till later next week at the soonest.

[bwilson4web]

Originally Posted by orange4boy

. . .
Have they figured out what makes them short out? . . .

That remains an open question. I found one Japanese paper about voids in the potting compound and high dV/dt leading to coronal discharges in the voids. But the problem is once the internal short starts, it pretty well wipes out the initial fault ... for folks with ordinary means.

Originally Posted by orange4boy

. . .Electric motors are notoriously robust, their main enemy being heat. In an oil bath I suppose debris might also pose a hazard.

I've seen some pretty rank oil samples and suspect two things:

1. manufacturing debris - my 5k transaxle oil change showed a small amount of metal shavings. Leave them in for 60k miles and who knows what damage they might do.
2. micro-dieseling - admitted a long shot, I suspect high-speeds lead to micro-dieseling and accumulation of combustion by-products in the oil. These are conductive.

Originally Posted by orange4boy

. . .Is there a fluid cooler on these? Who winds them? I'm guessing it's Nippon Denso.

No idea of who makes them but there is no fluid cooler and my temperature measurements indicate none is needed.

Originally Posted by orange4boy

. . .I found some OEM shop manuals on ebay. I guess I should get the 2003. They seem to be about $130-150 a set.

That seems to be the going rate for used manuals. I bought mine new for double that.

Bob Wilson