2010 Prius Brake, ABS, Traction Control Lights On

The lights that you have on would not be associated with any engine fault codes, just brake/skid system trouble codes. It seems the handheld scanner you used did not show you those.

The good news is, you don't need a scanner at all to get brake/skid system codes. You can do it like this, and then we'll know why those lights are on:

Blink (a/k/a Flash) Codes – How to. | PriusChat

 

Why yes, if you have Techstream, no point fiddling around with anything else....

 

Just one possibility: do you have anything near-constantly plugged into the OBD port. Ours had similar symptoms, and the apparent culprit was a ScanGauge II always plugged in.

 

My ScanGauge II has been plugged in since 2010 with no issues. (No, I haven't had the same car since 2010. The ScanGauge was plugged into my Gen 1 from 2010–2016, and has been plugged into my Gen 3 ever since, except times when Techstream is plugged in instead.)

So the issue Mendel noticed isn't necessarily inherent to having something constantly plugged in at that port. It may have something to do with the way it's plugged in, how much bouncing stress the plug puts on the connector while driving, the condition of the pins, or something like that.

Certainly, if you do have something plugged in there, and if you unplug it and the codes go away and don't come back, that may suggest there was an issue of some kind. But if there is, and the thing plugged in was something you want plugged in, there might also be a solution.

 

I think the problem he was referring to is that most anything plugged into the OBD port is powered ALL the time.......and can cause the battery to go dead or wear out sooner.

As for the original problem, could be a wheel speed sensor problem with one of the front wheels.

 

No, the SG didn’t draw power when car was off. Dealership mechanic noted his Techstream connection was dropping when he jiggled the cord, suggested I discontinue SG use as a test. It worked.

again, this is just one possibility; it did have sim symptoms: work-to-rule brakes, various brake/traction warning lights, and check hybrid system warning.

 

As shown in post #7, the car has clearly identified a speed sensor problem with one of the rear wheels, namely the one on the right.

The issue people sometimes run into with OBD-II plugged in is interference on the communication buses. I have experienced that (and posted about it) when I had a cable built with unplated pins. It caused no problems when it was new, but once it had a few years on it, could cause the car to erupt in warning lights and Uxxxx codes the instant it was plugged in.

Devices that are long or heavy (or have cables with long, heavy plugs on the end) can cause similar effects because their constant bouncing while driving fatigues the terminal springs in the car's DLC3 connector, until some of the connections are bad.

It's true that pin 16 has 12 volts all the time, and some OBD-II devices don't implement a very good sleep mode, and will drain the battery noticeably when the car's off. A ScanGauge doesn't draw zero current when it's asleep, but it's extremely low.

The data sheet for the ELM327 protocol chip has several pages toward the end about how to build a device that will have a very low-consumption sleep mode. Some of it is just a matter of the right programming to use the sleep features built into the chip, and some involves using more expensive other components around the chip. While there are cheap OBD-II gadgets that skimp on those details, the Linear Logic folks clearly spent the money to do it right in the ScanGauge.

 

Same story here, except only since 2015. The point being, a ScanGauge doesn't normally cause trouble.

 

Speed sensor is in the wheel bearing; the EBay item is just the wiring harness. If the sensor is bad, I think your only recourse is to replace the bearing.

As a test you might be able to disconnect both rear wheel speed sensor wiring connectors, and temporarliy run jumper wires, so that they're swapped side-to-side, see if the car then reports a problem with the other side. If so, it could be a problem with the wiring harness.

 

That's right.

As with any time you get any trouble code from a computer in a car, you have to remember that computer has no way of knowing why it doesn't get the right signal from that sensor. Maybe something is wrong with the sensor itself, or maybe the sensor is fine and there's a fault in the wiring from there up to the ECU. (In rare instances, it could be the ECU itself that has a bad input where that wire connects.)

That's why there's no such thing as a trouble code that means "go replace this thing."

There are only trouble codes that mean "go find out why I see such-and-such abnormal condition involving this thing, and once you know why, fix that."

Turning to those trouble codes in the repair manual will take you to steps that can be followed to help pin down where the actual issue is.

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