advice needed: traction light on full time

Yes, hot brake discs. If they get really hot, they can also warp, which might make your steering wheel shake when you brake,since it's the front brake rotors.

 

With the rims solidly bolted to the rotor heat gets transmitted to outside of wheel pretty efficiently. If the wheel is extremely hot be careful if touching the rotor, it'll be worse, lol.

With our car I think we could drive all day and the front wheels would only be a little warm. Your case does not sound normal, and is strong suspect for low mpg too.

Yeah get the brakes thoroughly checked: pad thickness, caliper pin lubrication, caliper piston not seizing in bore, rotor parallelism/thickness.

Be careful who does it, preferably Toyota: the electronics can be upset, or even piston ejected.

 

If your steering wheel shakes when brakes applied to cold discs then the damage has been done. They'll need to turn your rotors or replace them if they are too severely warped.

 

You still have traction light on? Yeah, it could be something in the car's electronics malfunctioning, causing the brakes to drag, considering all the symptoms. You mentioned "hill hold" not working too? Frustrating. All I can think is verify the mechanical condition of the brakes is ok, and then have the electronics checked. Seems so far like they are not able to diagnose properly, but willing to take your $'s.

 

It's not really possible to test brake drag on the fronts, due to the wheels being connected to the transmission. To turn them will always take some effort, so hard to tell. Still, if your wheels are very hot to the touch that's a good clue of drag.

If you've got 3mm remaining pad thickness that's not very good. 1 mm is the bare minimum, but I tend to be more conservative, would be thinking to replace pads soon. 3 mm remaining indicates brakes with lots of wear, and it seems to me less able to dissipate heat, prone to wear at accelerated rate for the remaining thickness.

To really see their condition the caliper needs to be pulled off and the pads examined directly. It's also imperative to check the caliper pin condition: they should be pulled out and regreased. If they're drying out it prevents the caliper from "floating", being able to move side-to-side. If that's the case you might see more wear on one pad than the other.

Anytime the brakes are opened on the Prius it's good to disconnect the 12 volt battery negative lead. It's possible for the car to try to pressurize the brake system, especially when driver's door is opened. After re-assembly of brakes and before reconnect of 12 volt negative cable it's a good idea to pump the brake pedal several times, to pressurize the brake lines, avoid the car's electronics getting upset.

 

Yes, but make sure the garage disconnects the 12V battery prior to working on the car, and does not allow air to enter the brake hydraulic system at the brake calipers.

The purpose of having the brake pads replaced now is to have the mechanic inspect the caliper and the caliper slide pins to determine why the wheel is binding. If the pads are worn to 3 mm they might as well be replaced. It is likely that the inner pad is worn more than the outer, if the wheel is dragging.

 

Be careful with choice of caliper pin grease. Toyota uses the expression "lithium soap base glycol grease". In North America "Sil-Glyde Brake Lubricant" is an alternative, commonly used caliper pin grease. The correct grease looks kind of like Vaseline or silicon dielectric compound. If the shop is Toyota they should be using the correct grease, Toyota makes a special grease for that application.

 

If Toyota dealership can't resolve a brake issue I think you need to talk to someone higher up in Toyota. Hopefully they will listen and get something done for you.

Codes showing, the initial car wash incident, something is up.

 

i wonder if there's an ecu problem, causing light brake pressure?

 

2013 Prius ,isn't this still under warranty