Mechanical or electrical?

I'm having a problem with my '01 Prius (with 99868 miles) that, after 8 years of successful troubleshooting, I can't figure out. It started with a humming sound coming from the front end that I thought was the tires, brakes, or something else. After checking tires and other stuff for about a month with no improvement (we only drive it about once or twice a week, usually a 30 mile round trip) I started it up one day with a new symptom.

It was about 10F outside. We had had heavy snow the week before and I had cleared a bunch of frozen road slush out of the wheel wells. When I started out there was a mechanical "clunk", and driving down the road there was a sort of rubbing sound from the front. It increased in volume and became more of a "howl" as the speed went up but was unrelated to engine RPM, just speed. Engine and battery functions all seemed normal so I just figured that I had either missed some ice that was rubbing on the drive shafts, brake shields, or something. When coasting to a stop the car didn't seem to go quite as far. Despite driving for 30 miles, 10 miles at low speeds, 20 miles at highway speed, hard acceleration, hill climbing, etc. the sound never stopped. Halfway through the trip I even jacked up each side of the front end to see if I could find anything rubbing. Nothing!

When I got it home I just parked it until the next morning. Next day I jacked up the entire front end and tried to start it but the 12-volt battery had gone dead. This had happened in previous years when the temps were really low. It seems that the charging system for the accessory battery isn't temperature compensated, so it never reaches a full charge in the winter. I grabbed a spare battery, took the half-frozen one indoors for charging, and jumpered the fresh one in its place (I had done this before in previous winters).

When I started the car and put it in drive with both front wheels off the ground the speed would only climb to 22 mph, so, although it still seemed to make the rubbing sound, I couldn't get it to spin faster despite "goosing" the throttle. I figured that either the traction control kept it from spinning with no resistance or I had the old problem with the HV computer connection to the throttle sensor that I'd had in previous years. So I undid the accessory battery and unplugged all 5 plugs going into the HV ECU (the throttle sensor connects to H14, the left-most plug). I plugged stuff back in and reconnected the 12-volt battery (this had always worked before). Starting it gave me a Hybrid System warning onscreen but it started and still spun the wheels at up to 22 mph. So I jacked the front tend back down after inspecting everything.(couldn't find anything wrong when rotating wheels, checking for bearing play, brake noise, shields loose, etc.).

Next I tried starting again and although the engine fired I still got the Hybrid System warning so I undid and redid the HV ECU plugs and battery again. Next start gave me just a Power Steering System warning (even though it was working perfectly beforehand and it's on it's third rack). Undid and redid plugs again and this time got just the Hybrid System warning and the car wouldn't start! I took the computer inside and dabbed an anti-oxidant gel on each terminal pin. Tried it again with the same results. Error codes on the OBDII show P3100, Hybrid System Malfunction (really helpful!!).

So is this a mechanical problem with the trans-axle (a posting I'd read here) or motor generators that is sending a shut-down message to the Engine ECU? Because of the transaxle posting I opened up the level check port on the transaxle and ATF level was perfect; no sign of discoloration. All I get on the dash is a nice bright display of an HV Problem icon, cold temp icon, brake indicator, but no READY light. I even tried putting the trickle charger on the battery terminals as I start it to make sure it's not just a low 12-volt battery. I now can't even drive it to the shop. Any Ideas????

I can't figure out if this is electrical, mechanical, or both. Why would something like maybe a bad bearing shut down the HV system? Why won't the engine fire? Why would some other new HV system problem crop up mysteriously when this sound occurred?

 

Thanks for the feedback!
All of the plugs are in place and seated. And yes, I always disconnect the battery and wait before messing with the ECUs. The scanner I used is a neighbor's "Actron Elite AutoScanner Pro". When I try to erase the one DTC I get the car gives a single beep and the code is still there when I rescan. Maybe I'll try to erase them, wait ten minutes, then restart and scan?

There was one bad wheel bearing up front (due to a fender-bender accident that got me this salvaged vehicle for only $5500 back in 2002) but it was replaced about 3k ago. I rotated all of the other wheels to check for play or noise. Nothing. And the noise didn't increase with braking. I'll let you know what happens with trying to erase that code.

 

OK, I tried the amended process with erasing codes and the result remains the same. No start, same P3100 code. I neglected to mention that the dash also has a "check engine" light on. This came on when it no longer would start.

The only thing that makes me think that the MotorGenerator2 stator winding could be the culprit (despite normal performance) is that when I removed the HV ECU and inspected the HV ECU connecting pins, connector H10 (right-most one), which deals with the MG's, had a couple of pins that had circular spots on them that looked like possible arcing.

I'm thinking of next removing the engine ECU next and coating those pins with anti-oxidant. 10F sure is lousy weather for car repair! Maybe magic will happen and it will start when temps are above freezing

This has been a reliable car up to this point, despite the original inverter non-continuity (that made the Toyota Master Mechanic throw up his hands and send it off for insurance auction - thanks Toyota!), the steering rack I had to replace, the bad wheel bearing, the recalled engine ECU replacement, the recall for battery inspection, the $150 I had to spend to have trans-axle fluid replaced, the throttle non-response (that happened 3 times and was fixed by unplugging and replugging H14), and the fact that this damn thing can't start without HV system power. Pre-80's cars are looking better than ever!

 

Thanks for the replies and ideas. But I have to admit that I'm an old-school kinda guy. My dad, who would be 103 this year if still alive, was a mechanic. He worked for car dealerships, diesel trucking companies, ag implements, and the local Montgomery Wards small engine department. He taught me how to fix anything pre-computer, mechanical, fluids, electrical, you name it.

And I've spent many years troubleshooting computer hardware and operating systems for friends, neighbors, and their friends. So when it comes to combining those talents, first I look for mechanical system problems, then the most obvious electrical problems like poor continuity.

I got this car from a scrapyard back in 2002 since the top Toyota Mechanics, flown in from CA to WI, couldn't figure out its no-start problem after a small but body-mangling crash. They couldn't make sense of the codes (sound familiar). Since they figured out that it ran with a replacement inverter from another car, they said it needed an inverter and steering rack. That cost, coupled with the $7500 in body work already done, condemned it to an insurance sale. Since the inverter was already out, I opened it and checked the connections between the inside and the plugs on the outside. 3 pins didn't have continuity. After 15 minutes of diagnosis and 45 minutes to put it back together I had a working car with 30,000 miles for $5500.

Needless to say, despite the noisy front end symptom, I'm reluctant to think this failure to start is related to a sudden failure of a motor-generator, especially since everything was running normally right up to that point. At this point, if increasing continuity at the connections doesn't help I'm tempted to start fixing the car with a 2lb.ball-peen hammer.

If cars these days are headed increasingly toward requiring a PhD in electrical engineering with associate degrees in software design and digital troubleshooting I think the era of backyard mechanics is truly dead. Physicists don't even fully understand what an electron looks like, whether it's a particle or standing wave, where "charge" comes from, etc. I tend to avoid just buying another "black box" that can magically tell me something that may or may not be relevant IF and ONLY IF all the connections are intact. I've always told people, "if you can't maintain it or fix it, don't buy it". I guess I've learned my own lesson!

 

I'm certainly well aware of the fact that others may know a lot more about the Prius, or DTCs, etc. than I do. That's why I started posting to the forum. But you'll note that, unlike the symptoms I could describe on a pre-80's car that would yield loads of experience-laden responses and suggestions, the best I've gotten here is an educated guess that my car is essentially dead.

I'm sure digital codes may be helpful when everything is well-connected and the engine runs, but finding out that the Gen1 and Gen2 Prius may have a stator winding or trans-axle defect makes all the codes more or less pointless. I know from experience with this car that Toyota will do everything in its legalistic power to squirm out from any expensive obligation to stand behind its product - unless of course you buy it new with an extended warranty. Telling Toyota that their "master mechanics" were unable to diagnose even a simple connector discontinuity didn't help my case. Even the techs were unable to make sense of the DTCs without the wiring intact. If you'd like the full story on how I got this car just click here for a PDF.

I'm quite happy I got 8 years out of this car, especially for what I paid, but I'd never consider another hybrid.

 

Yes, I'll probably try to find out exactly what's wrong, eventually, when the weather warms up a lot. I don't think the codes are "pointless", possibly just meaningless to all but Sherlock H. Mechanic. I tried clearing the codes with the scanner I borrowed but only the one came up and that wouldn't clear anyway. If there's some other tool required and it doesn't directly fix the problem I think that all I gain is knowing which parts to sell, and which may be defunct, as I "parts it out" on Craigslist. Taking the trans-axle out is something I'd do either way, since I have the manual, but it will have to wait. Today I'm looking at 40+mpg used cars in my vicinity that will be good winter "beaters" to supplement the EV Porsche. Their cost is far less than a trans-axle repair. I'm sure there are Prius owners out there who have had glorious days with their car, as I have, but entropy and lack of cash have taken their toll.

 

I was wondering how waiting 10 minutes had anything to do with anything! When I turn the key I hear 4 relay clicks coming from the rear, no READY light, no engine spin. On the dash we have a check engine light, brake light, low temp light, and the hybrid system warning. Do I really need to buy a different scanner just to detect and delete some possibly different codes?

 

Thanks everybody!

I've come to 3 conclusions:
1) I probably do need trans-axle work that I cannot afford
2) I probably caused the codes that I cannot currently read when I ran the car with the wheels jacked up (seemed like a good idea at the time if I wanted to hear the drive-train without road noise) which are causing the car not to start
3) I can't fight 8 intercommunicating computers at once, they win!

I am currently car-less until the shop nearby that rebuilds Geo Metro's is done with the '97 5-speed they are working on. Great market for these things right now. 1200 lbs. less weight to haul around and only 1 computer. At my age, and with my level of skill and patience, sometimes simpler is better.

I'll try to borrow a Scangauge II so I can figure out what to sell and what can't be sold on the Prius. Bob Wilson on the Yahoo Prius Tech Forum offered one to rent if all else fails.

Thanks again!