ABS and ! Lights

Thee ABS and (!) lights indicate that the control computer is not seeing the signals that it expects from the ABS sensor on the front wheels. That it's intermittent indicates to me that you may have either a failing/corroded ABS sensor on one wheel, or a damaged wiring harness from sensor to computer that intermittently gives you the fault. You may need to take the front wheels off and follow the wiring harness to the ABS sensor; do some cleaning as needed, look for damage or anything which is out of sorts.

Techstream is good, but it isn't all-knowing.

I see you're in FL, and it's a 2004 Prius (which is Gen II). Have a look in the Gen II forum, too...

Good hunting!

 

At least, that's one of the couple hundred things those lights can mean.

If you do not have a scan tool that works, there is a method using a short piece of wire to get the brake ECU to report the trouble codes as blinks on the dash lights, which you can count. That gets you some of the needed information quickly, without depending on a scan tool and without having to wonder whether the scan tool you've got is behaving right.

The two-digit codes you get can be looked up in the Repair Manual, as described here. Or you can post them here on PriusChat and see what members know about 'em. Be sure to include which code was blinked on which dash light, because the code numbers can overlap, and they'll mean different things.

 

Oops, sorry... you own an '04, but you're working on your daughter's '02 Prius. This is the right forum. Sorry about that, chief.

 

Techstream is definitely supposed to work, and if there is an issue it might be specific to the particular dongle you're using.

But if your dash lights are ones driven by the brake ECU, it has the ability to give you the trouble codes through light blinks that you count, so you'll be able to get the information you need for the moment, without having to wait until you've got any Techstream issues ironed out.

 

Well, you already have Techstream, but for some reason it doesn't recognize the 2002 Prius. That the ! and ABS lite shows up "intermittently' points to a wonky ABS sensor on one of the wheels. Not a horribly difficult job to replace the sensors, but the toughest task will be to get the sensors out. The pictures on the RockAuto.com website are helpful, as are the diagrams on the ToyotaPartsDeal.com website. ABS sensors are integral with the rear bearings. If you feel you're out of diagnostic options, an option is to bite the bullet & have Toyota do the diagnosis (and depending, maybe the repair) for you. Certainly ask for a printout of the diagnostic report that they get from their in-shop Techstream. If Toyota does the repair, then Toyota is on the hook if it ever happens again.
Good luck!

 

A wonky ABS sensor is one of the couple hundred reasons those lights can come on. Reading the trouble codes will reveal whether it is the reason these lights are coming on in this car.

Whenever there is some difficulty using a scan tool to retrieve the trouble codes, it is useful to remember that the brake ECU can always blink out the trouble codes on the dash lights, with no scan tool required.