Greetings, all. I have had my first major problem with my wife's 2002 and it is probably mostly my fault. Watch those inverter coolant levels, guys! It began with a hybrid error while my wife was driving in town. The system became unresponsive until restarted, then I saw the inverter coolant was pretty low. I can't explain why I didn't add water to bring it back up. Anyway, we nursed it home (my day for bad decisions, I know) and it died in the garage. The engine would start and the code read P3125 - erasing the code cleared the hybrid warning as well but shifting to reverse immediately brought in the inverter failure code and the warnings. I ordered a replacement inverter from a wrecking yard, put it in, went through a half dozen attempts to bleed the coolant and finally saw steady coolant level and coolant flow. Better now - with the old inverter the battery would charge on startup but could not stand to be shifted out of Park. I would also get the P3125 if I revved the engine in park and suddenly let off the throttle. Both those indications have stopped. But now I get P3125 the moment I lift my foot off the brake in reverse or park. If I get real desperate I have a 2002 of my own to swap inverters with but I would sure like some sanity... I seem to have run fresh out. Thanks a million!
According to my manual (2001), P3125 pertains to the DC/DC converter (which is one component of the inverter assembly) can mean a lot of things. See if you can retrieve the 3 digit "inf" subcode that goes with the code. 263, 264, 265 are possibilities to do with the DC/DC converter, but only 264 would definitely point to a problem in the inverter itself. A lot more codes (266 to 345 or so) point to other specific problems with the inverter or associated circuits. -Chap
Thanks, Chap. I apologize for being so late in following up, but a lot has happened. The car in question, my wife's 2002, is now a project car. We got a good deal on a 2010 Prius so she is stylin' now! I wish I could get the sub-codes but I would have to tow the car to the dealer (which does not have a good hybrid tech); get the codes/sub-codes read, be told it would cost zillions to repair, and tow it back. For about the same amount of money ($300, in this case) I bought an inverter from a wrecker in Maricopa AZ. The replacement inverter is different; the original allowed me to start the system, the battery charged, but if I held the throttle down in park to rev it a bit and suddenly released the throttle it would error out, and it would error out if I put the selector in reverse or drive. The replacement does not error in park or if I shift into any "gear" but if in reverse, drive or Brake it errors out the moment I let off the brake. I tried the replacement inverter in my 2002 and it works... at least enough to let me back out of the driveway and go as far on the street as I dare without a tow vehicle around. So there is something else wrong besides the inverter. I reinstalled the original working inverter in my own car to minimize the uncertainties tomorrow and will reinstall the replacement in the dead car tomorrow. I am thinking the next step is to swap batteries between the two. The dead car only has 130K miles on it but the problem could very well be with the battery pack. It got the sealant around 60-70K miles but that doesn't mean the battery is bulletproof. Any other input is certainly welcome! Mike
Prius-aware scanner - there are at least three, miniVCI, ScanGauge II, and the Android. Half a dozen control computers operate the car and a Prius-aware scanner will let them tell you what is wrong. Prius shop manuals - Volume 1 translates the computer codes and symptoms into a diagnostic tree. Volume 2 covers how to effect repairs. The wiring diagram handle what signals flow over which wires. Bob Wilson
Thanks, Bob! I didn't think the NHW11 allowed access to conventional scanners beyond the Engine unit. Somewhere around here I have a Graham Davies miniscanner but since I haven't needed it in ten years I am having trouble remembering where I stashed it. I do have the Toyota manuals.
Owch . . . inverter subcodes is one thing the Graham miniscanner fails to report. But we can at least check the other, usual suspects. Bob Wilson
Raskolnikov! At least I have something to work with and time to work with them. I am putting the now-tested inverter back in the project car this afternoon. I will pencil in battery swap for next weekend. The progressive nature of the faults - one transient a month or so before and then the meltdown (but not a turn-key-off failure) suggests a fault in the battery. If that doesn't do it I will have to rig a trio of jumper cables from the dead car to the MG2 in my working car to rule out or confirm that part. This is so much stressful with the car officially off the road. I sure do appreciate the help. I am really pleased by the ease of the inverter replacement. The first time it took me about an hour and a half to remove (once I got the cowl stuff out of the way) and the same to install the replacement. Those times are down to under an hour each way now. I'm getting really practiced in purging the cooling loop... I never did get it to work the way the manual showed.
The part that doesn't work is running the hoses from the nipples back up to the reservoir. The air just doesn't like to bleed if there happens to be a blob of coolant ahead of it. By running the hose (I do one nipple at a time) over the bumper to a container the air flows out readily without trying to run the pump. There is still that last little bit that hides somewhere - about the difference between "low" and "full" - and shows up after driving around the block though.
The code 3125 from my experience will often point to the transmission itself. It should have nothing to do with your hybrid battery system..Just my 2 cents.. Keep us posted..
Hmm. The battery is relatively easy to swap so I will probably do that. I agree that if it is not battery it is likely to be MG2 in the transaxle. Good news / bad news... I can get a replacement transaxle for around 1/3 to 1/2 the price of a reman battery but I don't look forward to doing a transmission swap. My thinking is that the inverter code is popping up because the inverter is unable to drive MG2 (based on when it errors out - when it tries to control MG2). That could have been a defective inverter - ruled out - or inadequate supply or excessive load. Good thing it is a project car now!
Okay... but I reserve the right to suppress all the pictures of me crying with my head in my hands. My stupid brain is dredging up another vote for the transaxle. For a few weeks before the big failure I noticed the regenerative braking was producing a notchy sound instead of the light whine. It hit a resonance around 20 mph as a smooth growl. I had assumed it was the inverter doing it but it also fits MG2 failure.
3125 in my limited experience is the transaxle. I don't think I've ever seen it be anything else but this could be the first.
It sure is looking like the transaxle. I brought home a peak hold amp clamp (Fluke 376) but I was foolish enough to think I didn't need the flexible loop. Anyway, I got current readings on two of the three MG2 leads. In park they were in the 1 amp range; in reverse with my foot on the brake they were 6 and 13 amps; when I let my foot off the brake and let the error appear I measured 20A on one lead and 54 on another. I haven't measured the currents on my working one; maybe I can do that tomorrow and post the results. 54A sounds like a lot for just trying to back up with my foot off the accelerator. It really would be nice to have a benchmark on that, using widely available equipment.
Another easy thing to try is to drain just a little fluid from the transaxle pan and smell it. If it smells burned and looks blackish that's another bad sign. Just FYI changing the MG2 is really not a bad job..
On the lines of this, I thought this was an excellent write up on the GEN1 Prius transmission with pics. Prius 1st gen - Replacing an MG2 (electric motor) TomK
I don't understand what is the point of replacing MG2 by itself, vs. replacing the entire transaxle. Can you buy a used MG2 assembly for less than you can buy an entire used transaxle?
This is what seems to be the family of options: The canonical way, for a difficulty benchmark: drop the engine and tranny, remove old tranny, attach replacement tranny, reinstall. More work than the benchmark: drop engine and tranny, remove old tranny, separate into halves, replace the MG2 half, reassemble, reinstall. Arts Automotive has an article with pictures using this approach. Ended up deciding never again because the process of correctly adjusting bearing preloads requires repeated partial assembly and disassembly using select-fit shims that ship from Japan. Car tied up a bay in their shop for a month. Less work than the benchmark: the thing that dies is the MG2 stator. Take off wheel and MG2 endplate, pull out rotor and stator, pull rotor out of stator (strong magnetic fields!), harvest good stator from another MG2, insert rotor (strong fields!), reassemble, put endplate and wheel back on. Jack Rosebro worked out how to do it and Carolyn at Luscious Garage has put up a video. Big win on labor because you're not dropping the whole engine/tranny, and you keep the original rotor, bearing, and shims selected at the factory for preload. The MG2 resolver is a part critical to powering the motor correctly, and is located inside the endplate. The first write-up I saw describing the technique said Jack Rosebro had worked out how to do it without disturbing the resolver adjustment. That's all I know so I don't know if that's easy or tricky, but it's a thing to think about. Maybe all it comes down to is knowing which bolts need to come out to get the endplate off, and which ones might have to do with the resolver. -Chap
