Three warning lights come on when I go 70+ mph

That's a crock of BS.
Likely that something was damaged with the wheel speed sensor near the replaced bearing.
If the shop that did that was not a Toyota dealer, you might have to find one for a fix.

Oh.....and it is likely that your basic brakes will still work like that but you really should get it fixed and you probably have a major safety system that won't work right when/if you ever need it.

 

The simplest explanation is usually the best. Most likely something got bent or skewed out of alignment when you had the wheel bearing replaced, and it's a small enough skew that it's not noticeable until the wheel is spinning fast enough. It's still something I'd get looked at, as brakes are very important when you are traveling at high speeds.

Regarding your shop saying they can't diagnose the issue if they don't see it: I had an issue that only occurred at speed in a previous car, and one of the mechanics took a ride in the car with me to find out the problem. If the mechanics at your auto shop won't do that, then I'd suggest going to a different shop or a dealer.

 

Its likely to be the abs wheel speed sensor that has either gone bad, or one of the teeth on the driveshafts teeth has removed. Suffice to note that such problems occurs when the right driveshafts aren't replaced. In some cases, the ring groves on the driveshafts, could be bugged with dirt, and would send the wrong signals to the wheel speed sensors.

Check if the sensors are are properly seated on the hub.

Some other tines, if one of the sensors is failing or bad, you'd ha e such a problem

 

You've had the same issue for 75,000 miles? Wow! Out of curiosity, since you've obviously had it for several years and haven't been bothered by it, why bring it up now?

 

Can hardly believe there are no codes. How do you know this is true? Just know that while the lights are on, it most likely means your ABS and VSC are not functioning. Likely people don’t often need these systems, but.

So they do not turn off until a complete stop, or turn off below 70 MPH? The prior being a much more important scenario. How’s the brake fluid level? (Kind of complicated how it is checked, with the accumulator sucking it down).

 

I think Toyota engineers would make sure anything that important would bring up a code, if it clears without action it is probably something minor just out of normal parameters, but me being me I would have to find out what

 

Replacing a wheel bearing or wheel hub on a Gen 2 can be done without total disassembly of the knuckle. There's a dust shield covering the abs wheel that has to be popped loose and slid inward out of the way to access the hub bolts. There's a small cutout about 3/8 inch long and 1/4 inch wide on the dust shied that the abs sensor "looks through". Maybe they used this method, but didn't align the dust cover completely right during reassembly. Would only require a 10mm socket to remove the abs sensor and look down the hole to check for a clear view of the abs wheel.

 

Codes should stay in the history, unless there are a number of on off cycles when the code is no longer present, ie. Check engine light for gas cap accidentally left off. Since the OP notes hardly ever triggering the light by reaching 70+ MPH, I’m not surprised if the code disappears after a while. But it should be in the history until the requisite number of cycles without being triggered again are met.

(At least I think that’s how it works...)

 

UNLESS you have tried a panic stop on wet pavement, you haven't really tested the part that is failing. IE the ABS system.

We all drove cars for a LOT of years without ABS at all so you might be fine. Then again maybe not.

It's your call......but I'd say you really have already made it by driving it in that condition for 75K miles.

 

here is a possibility.

mismatched tire sizes, under inflation, or significant differences in tire size can cause your issue. if tire #1 is larger than tire #2 (lets say it is 10% larger just to make the math simple) it will give different speed readings to the skid control unit. at 20mph tire 2 will say 20 mph and tire 1 will say 22 mph. it is not a large enough difference to meet the threshold (in reality that is a large difference but this is just for explanation) but when you are at 70 mph tire 2 will say 70 mph and tire 1 will say 77mph. the threshold happens to be 7mph difference and the skid control will try and compensate. when it does so it illuminates the traction lights until the speed difference falls below the threshold again.

to confirm this you will need a computer that is capable of viewing live data from the ABS computer. you will just need to watch the individual tire speeds. you could also switch the front tires with the rear and see what happens. the rear tires have less of an impact on skid control computer than the front.

this type of error usually does not set or store any error codes because the skid control interprets it as a loss of traction, not an error. I would still see if there are any codes because they can provide vital information.

Hope this helps!

 

Doesn't this tire size difference also overheat the differential?

 

Not really, no, because the Prius differential doesn't have any limited-slip features built in to heat up; it is essentially as frictionless as any of the other gear elements in the transaxle. And if the size difference happens to be between two rears, or a front and a rear, then not at all, zero.

When the Prius traction control wants to limit slip, it can do so directly by using the ABS actuator to brake a slipping wheel.

-Chap

 

The likely-revealing test would be to plug in Techstream or a ScanGauge, Torque phone app, etc., and watch the four wheel speeds (ok, have a passenger watch them!) while zipping down the highway at 70+.

Probably, as already suggested above, it will show a difference between the RPMs of the wheels.

-Chap

 

I don't see that in the posts in this thread at all.

Under "normal" conditions it might not be a serious problem......but it might be VERY serious if you need ABS sometime and it doesn't work right.

 

Off-topic, but does anyone actually teach proper use of ABS (crash-avoidance steering)? I certainly never learned anything about it when I was learning to drive, but it might not have been very widespread then.

 

Me neither. I suspect they do now.

STOMP, STAY, STEER.

It is pretty easy to test/practice in and empty parking lot when the pavement is a bit wet.
I think everybody should do that at least once.

I doubt they actually practice it in "driver's ed" because of liability concerns.