Stop turn it off then back on and it stops

The device you're looking for is a "Mini VCI" and the diagnostic software is called Techstream. It's sold cheaply via eBay and probably elsewhere. I think you can only run it under Windows and the ideal is to have 32 bit Windows XP, but it can be made to work under other windows versions as far as I know.

 

A 2002 with those problems could get expensive if fixed by a dealer.
PS rack could be worn,or maybe just low on fluid



12V
bbabatbattbattebattebatterbatterbatterybattery
mmymy
bbebe
low

 

Things like this might happen to any 18 year old car.

Spend some time reading threads about similar problems, realizing that some of your "symptoms" might be totally unrelated to the major problem.
Then get the 12 V battery tested.

After that, there are several things that could be acting up and right at the top of that list is the high voltage hybrid battery.

I suggest that you need to pay for a proper diagnosis at a Toyota dealer, since the odds are that you will NOT be able to effect a fix yourself even if you can determine what is wrong. The news is likely to be bad.

 

My '01 was having some issues starting when cold. The IC engine would start then stall. All it needed was to have the throttle body cleaned.

 

A shaking steering wheel is common in a Gen1 Prius (2001-2002). It is usually due to the Power Steering Sensor (a simple variable resistor) wearing out. An active user here, Bob Wilson (bwilson4web), has expertise in this failure mode. If you have an Android phone or tablet, DRprius or Torque are apps that can be used to diagnose Prius problems. I have used the MiniVCI as well, but it is a bit "techy" to get it installed correctly.

JeffD

 

Fiddlesticks! I loved my 2001. Drove it till it met the east end of an eastbound Dodge Dakota at 15 years and 23x,000 miles.

You're right that it will be very helpful to have a way to read the diagnostic info from the car. The way that will have the fewest limitations is to put Toyota's Techstream software onto some old beater laptop, and get a "J2534" dongle to connect the laptop to the diagnostic port on the car (under the dash, just above your knees). The "Mini VCI" above mentioned is one of those J2534 dongles. You'll see some others mentioned around here, like VX Diag, or Openport 2.0, if you look. The one Toyota officially tests and stands behind is the Drew Technologies Mongoose Pro, but it's pricey.

Now, here's a thing about the Prius Gen 1:

A lot of different things in the car depend on sensing the position of something, and feeding that position to a computer, which uses that information to control something.

The accelerator pedal moves a position sensor, which the computer uses to know how fast you want to go.

The steering system uses a position sensor, which the computer uses to know how hard you are turning the wheel, and to decide how much to assist you. (How do you use a position sensor to find out how hard you're turning something? Well, you put a stout-but-slightly-twistable section in the middle of the steering shaft, and mount the position sensor so it measures the position of the top end relative to the bottom end. Poof! It's a torque sensor.)

There are three flappy doors inside the heater/AC that select (1) whether the air comes from inside or out, (2) how much it gets warmed, and (3) which outlets it flows to. Each of those three doors is controlled by a little motor and has (ta da!) a position sensor so the computer can move each door to the right position.

All of those position sensors in Gen 1 work the exact same way. It's about the simplest approach, a variable resistor (a/k/a potentiometer, or "pot"). Take a long strip, or curvy strip, of something that has electrical resistance, put a fixed voltage across it from one end to the other, say 5 volts at one end to 0 volts at the other, and have a moving contact that picks up the voltage at whatever point on the strip it is touching.

It's the same technology as the volume and tone knobs on an old stereo. Have you ever used a really old stereo and noticed when you're twisting the knobs, it makes nasty staticky noises? Potentiometers get oxidized/"dirty" over time, and then the voltage jumps all over the place as you move the movable part, instead of just changing smoothly from one end to the other.

Naturally that's bad news for a position sensor in a car. When the computer gets a position signal that's jumping all over the place, it "looks like" the thing being controlled is jumping around, and the computer will try to shove it back toward the intended position (which makes it really jump around).

When that happens with one of the heater flap servos, it makes a sound like you've got a little mouse scrabbling around under the dash.

When it happens with the steering torque sensor, it makes the steering wheel shake. The computer is getting a spurious jumping-around signal that you're trying to turn the wheel one direction, then the other, so it's sending assist power to try to help you. Eventually it says to itself "you know, I think this signal is just bogus, I give up", and the light comes on, and there's no more shaking and it's just hard to steer, because the computer isn't giving any assist. You can turn the car off and on again and be back to square one, until it decides the signal's bogus again.

When it happens with the accelerator pedal sensor, and the computer decides it's bogus and doesn't trust your accelerator pedal movements, the car doesn't go much. It feels like a Big Hand reached down from the sky and grabbed your car.

All these things happen for the exact same reason, "pots" that get electrically noisy, and there's an effective fix. "Dirty" pots can be cleaned. The corner electronics shop has been doing that to stereos with noisy volume knobs for decades. Squirt some contact cleaner in there, twist the knob back and forth a bunch of times, all the nasty noise is gone.

In a Gen 1 heater flap servo, that's super easy. The servos are easy to get to (well, two of them, anyway), and the cases pop right apart with releasing some clips. A Q-tip and some contact cleaner and it's good as new.



For a Gen 1 accelerator pedal, the principle's exactly the same, but the wretched plastic case is glued together, so has to be carefully sawn open, then reglued after cleaning. Or save the fussing and just buy one.



For a Gen 1 steering sensor, the principle again is exactly the same:



The bad news there is that the ever-lovin' sensor is built into the steering rack itself. It is not difficult to remove from the rack for cleaning once the rack is out of the car, but getting the rack out of the car is a serious heavy-mechanical project.

Toyota did have a warranty extension that replaced a bunch of the racks for free (I got mine replaced that way), but we're beyond that now, so it's down to other methods.

Bob Wilson had some ideas about 'tin whiskers' and a way to clean up pots electrically without having to take them apart, which could be very much of interest with the accelerator pedal (to save cutting and gluing) or the steering (to save the difficult removal/reinstallation of the rack). I don't know how effective it turned out to be though.