P3125

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!

 

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

 

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.

 

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.

 

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.

 

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.