Hi all, I have lurked but haven’t found anyone that’s had my symptoms. I made an account to make this thread. I have a Gen 1 2003 Prius (couldn’t find a gen 1 page). My father bought it pretty much new in 2007 and I have since bought it from him. It’s at 377,000 miles right now and has been such an amazing vehicle that we now have four of them in the family. I’ve used this car for everything from doing farm chores, across country drives, hobbies, daily commute, etc. It’s been in a couple accidents and in the ditch a couple times. It’s not pretty anymore but I have a lot of respect for this car as it just keeps going without complaint and getting 40+ mpg to boot. For the past couple years it’s been sporadically doing this thing. I’ll be going down the road and all of the sudden it’s like the gas engine disengages from the transmission. The gas engine will be on and racing but all I will have is electric going to the wheels. The orange triangle comes on of course. When this happens I’ll coast to a stop. Turn the vehicle on/off three times which resets it and then continue on my way as if nothing happened. It seems to happen when passing someone on a two lane, climbing a hill, or during some sort of heavier acceleration when already at speed. It happens maybe once every few months. Anyone experience this before or have feedback? I’d think it was a mechanical slippage in the transaxle except that it resets itself. Feel free to move this post if this isn’t the best place for it. Thanks Solocam92 from Iowa
There is a Gen 1 forum, which is a little tricky to find, because it's a subforum of Gen 2 for hysterical reasons. I can report this to the mods so they can move it there. I would suggest just having the car's diagnostic codes read, and going from there. It is obviously detecting some kind of an issue, and going into a limp mode. You are resetting it to go a bit further until it detects the same issue again, but it would be better to learn what the issue is.
Just for giggles change the transaxle fluid? Check condition/quantity of drained fluid. I've no Repair Manual nfo for that gen though, and I'd assume Toyota says nothing in Owner's Manual. Here's info from Owner's Manual: The quantity indicated is likely more than what would drain. With gen 2 and 3 maybe 90% drains, and Toyota instruction for filling is (in a nutshell) "fill with car level, 'til fluid starts coming back out". Not sure if that applies with Gen 1, @ChapmanF might comment.
Yes, that's how it's changed and filled. Have to be a little careful because the transaxle coolant and oil drain plugs are near each other and identical. And it's always a good idea to confirm you can open the fill plug before opening the drain plug. However, just like in the later generations, this fluid doesn't do anything but lubricate the transmission and carry some heat away. It is not doing any conveying of power like the fluid in a traditional automatic transmission. If it were not there at all, the transmission would still work, until it didn't. The fastest, least guessy way from "I wonder why these lights are on and this stuff is happening" to "ok, now I have some idea what issues are being reported" is still to read the trouble codes.
Sounds like what you're describing is 'limp mode', when the car gives up on the main traction battery and generates all its torque using the gas engine. The engine revs at high rpm's to drive both the electric motor and wheels. (It's like the tiny spare tire, good enough to get the car down the road to be serviced.) The car draws on both engine and battery when accelerating, so perhaps your battery doesn't have a good enough charge to keep up under a heavy load.
I agree it sounds like limp mode, and will mention again that if you ask for the diagnostic codes, the car will tell you why it has chosen limp mode.
So, now it is time to tell solocam92 how to get the codes. One way is to pay a dealer to read the codes. Another is to get a cheap OBDII bluetooth enabled adapter from Amazon that plugs into the diagnostic port under the dash and then run an app like Dr Prius. A third way is to get (a pirated version of) the software, called techstream, that the dealers use and run it on a laptop. That way is more complicated but gives the same info that a dealer would get. (google techstream or search this forum to learn more)
Thanks for the replies! And thanks for letting me know there is a Gen 1 forum. I have not gotten any codes because when it happens it is usually alone the side of the road somewhere where I don't have access to a code reader. I might purchase a cheaper obd scanner to leave in the vehicle to pull any codes while alone the road. Regarding the limp mode. This has been a bit puzzling to me. The motor revs up and the fan kicks in overtime like I've read would be normally in limp mode. However, I learned the hard way that it's pulling from the battery. The first time it happened rather than pulling over right away I drove another mile at ~60 mph to a good spot to pull off. This inadvertently almost completely drained the traction battery and after I restarted/reset. I was left with an almost dead traction battery - It was showing one bar (25%) on the screen. It had a hard time getting started again after reset without the torque from the electric motor. After that I've been careful to coast and pull over asap.
Engine codes are stored and can be read at any time, not just when the car breaks down on the side of the road. As I understand it, limp mode disconnects the main traction battery, so it's not being charged or discharged. Once the car starts to go into limp mode, that's usually a sign you're ready for a new battery.
The hundred or so possible trouble codes reportable by the HV ECU do not all lead to the same kind of "limp mode". The details depend on just what went wrong. I believe there's a table in the repair manual that says more about what the "limp" behavior will be in each case.
