Traction control activating randomly

It's weird. That's definitely a bad SAS reading, right? You know the car was going straight, and I bet you hadn't just turned the steering wheel 366 degrees to the right.

But it's surprising to be seeing that on the third SAS in a row. But it did come from eBay. But that's still a pretty unlucky streak.

The sensor transmits its reading digitally. If it were some old-school analog circuit, I might be thinking "ok, some noisy electrical connection somewhere, makes the 0° signal look like 366°". But digital transmission shouldn't work that way; it should be more like, the ECU is getting the right message from the sensor, or it knows that it isn't.

So there is something very puzzling about this. But for sure, in that freeze frame, it's the steering angle reading that stands out, doesn't make sense with the rest.

 

Right, 'cause then it's just thinking "I've got no steering angle sensor, I'm useless", instead of thinking it has a sensor and the wheel is spun hard over.

That could be worth a try.

Well, this is the sort of issue that is weird enough, it's like asking a judge nominee how they'd rule on a case that isn't brought. I'm pretty sure if I were facing this issue, I'd find it hard, and I'd have the repair manual and the wiring diagram in front of me for hours, and I might be planning a sequence of things to test. That's just really hard to do over a forum, though.

 

If I had to guess, I'd wonder if in other models, where they sold the parts separately, they had too many customers coming back with issues because a tech had failed to mate the sensor properly to the centered spiral cable, and they just decided to do that at the factory and take installation questions out of the picture. But I'd be guessing.

 

I'm betting on the used SAS sensor may be the best answer here. I just replaced the SAS with an ebay knockoff and it worked for about 2 miles, then setoff the C1231 again as well as the U0073 (which I never had before). Now the TSC and ABS lights come on randomly. After I turn the car off, sometimes they go away, but then pop up shortly after starting to drive.

My original code was just the C1231 with the TSC light on. Luckily the TSC doesn't try and kick in while I'm driving, at least it hasn't yet.

dave

 

I just checked my 12 volt and it is reading 12.2. I wonder if that could cause the communication error. Have you checked yours?

SM-S908U1 ?

 

12.2 volts causes communication errors the way skipping your midafternoon snack causes you to keel over from starvation.

The repair manual doesn't even tell you to delay diagnosis for battery charging unless it's below 11. And that's a conservative number. In the ECUs that can give you diagnostic codes for low voltage, those thresholds are mostly around 9.5. And when you get those codes, it's not like you're getting weird ECU delirium; you're getting "I'm programmed to give you this code so you'll know the voltage here is below 9.5, maybe you'd like to check that."

In my experience, weird ECU delirium tends to set in around 7 volts or so.

12.2 is well within the range "12 volt" electronics are designed to operate on.

 

Any updates on this? I have the exact same issue using an aftermarket SAS. I also suspect crappy Chinese SAS so ordered a used OEM SAS. Should have it in a couple days. Since steering angle is communicated digitally over a bus, if they didn't terminate the bus properly it could definitely cause these issues. Fingers crossed. [I see random U0073 and SAS/ABS lights on dash, all of which get cleared after turning car off and back off. Sometimes the ABS system actually activates while driving straight - scary stuff]

 

Well, since Chapman shot down my idea of a possibly battery going bad, I decided to look into it further. It seems that I left my Autel OBD bluetooth scanner attached to the OBD port. I read a few posts saying that can cause communication issues. So far, all is well after removing scanner from port. I had it plugged in to verify that the new steering angle sensor was feeding correct info to the car.

 

What do the pins on that Autel dongle look like?

An old box I once built to simplify twiddling the Tc and Ts lines, built on a plug with unplated pins, worked great when I first built it, but later would cause rampant communication errors just by being plugged in.

Since I rebuilt that twiddler using a plug with gold-plated pins, it's been rock solid, I've even plugged and unplugged it with the car on, nothing glitched.

 

I'll have to look to see what the pins look like. Unfortunately it turns out that did not fix the issue. After driving a while yesterday the 2 lights finally came on. I'm going to the local pick-and-pull this afternoon to try and find a used Toyota part.

dave

 

It sounds like these guys are basically building random number generators and selling them as steering angle sensors.

 

I was thinking about this this morning on my drive in (while in Maintenance Mode because the Traction Control finally decided to enable itself the other night for the first time). Do we think it is a bad clockspring we are getting, or the actual SAS, or both? The reason I ask is that my original part that went bad ONLY setoff the Traction Control light. The newer part sets that off as well as the ABS?

I unfortunately went to my local pick a part yard and they didn't have any 2010-2015 Prius' in stock, so now I've got to find one online.

 

Well, the bogus readings that are triggering the traction control are coming from the steering angle sensor. And while the sensor physically mounts on the spiral cable, its wiring doesn't go through the spiral cable. It doesn't have to; it just has its own cable connection that doesn't turn with the wheel.