intermittent error pattern

Well, our 2018 Prius c has finally become cranky.

For about a week now, we get some errors popping up on the screen. Sometimes at startup, and sometimes after driving a bit.

And sometimes not at all- sometimes the car boots right up and drives completely normally.

Sometimes it reports "Pre-collision system malfunction"

Sometimes it reports "Headlight system malfunction"

Sometimes it lights up an ABS warning and the traction control warning.

Sometimes it gives a cruise control unavailable message.

Sometimes there is a combination of the above.

Occasionally when braking, the car gooses the brake on one wheel and shudders the pedal a bit.

None of this has resulted in a persistent DTC that I've been able to find.

Of note, I dug out my old PC with a hacked up techstream and discovered that... it really isn't going to be helpful going forward. (Old PC got too old.)

So now I've invested in an Autel AP2500E and begun the process with that tool, but nothing to report yet.

This should be fun!

 

I haven't worked out the common thread between all the errors. Doesn't even seem like there should be one, but obviously there is.

I have moderate expectations for the Autel. It didn't cost much. It might help, and it might not.

Installing Techstream on a newer computer is in direct conflict with my goal of not having a newer (windows) computer.

 

I don't think that was a dumb question.

In fact, it was overdue for replacement.

So I put a new battery in yesterday, and the problem has persisted. (I didn't have any real expectation that a new battery would solve this, but again... we were overdue anyway.)

Roughly 4 out of 8 trips since replacement, we got some combination of these errors. The others were error-free with the car behaving completely normal.

I'm going to carry the Autel dongle in the car to see if I can catch it acting up.

 

If I can't solve this one without techstream I'll go rent a laptop from the pawn shop.

(I say rent; I buy it. When windows acts up I sell it back and buy a different one. Been doing this for years and was hoping to retire that cycle...)

 

Right, the little Autel dongle combined with my phone has already made significant inroads to the problem.

Initially it wasn't finding anything, but this was due to my lack of familiarity with the tool. Apparently I needed to buy an extra software module to have it look beyond the basics. The version of the kit that I purchased allowed me to claim this extra module for free but that may not be true in every case in the future.

I drove my daughter to daycare this morning and the car behaved normally until I pulled into the parking lot. The combination meter beeped a few times and started showing a combination of the previously named errors, along with skid control and brake warnings.

After the drop-off, I ran the newly-acquired full scan on the car while it was presenting errors.

I was presented with:
ABS/VSC/TRC
C1238 Current, foreign object attached on tip of right rear speed sensor
C1466 Current, right rear speed sensor circuit
and
Main Body
B124B automatic high beam system
B124C high beam camera

I believe those last two errors are why I've seen the "HEADLIGHT MALFUNCTION VISIT DEALER" flag on the MFD. Based on some literature I found regarding that system, I understand that the automatic high-beam system is dependent on yaw rate data.

If the right rear wheel speed sensor is throwing bad data I could understand all of these other faults cascading out.

And wouldn't you know it? I had the right rear wheel bearing replaced last year.

Car isn't fixed yet, but I'm fairly encouraged by what the little Autel has told me so far. I don't get to take the car apart until tomorrow. Hoping I can clean what I've got and restore good data output.

 

Well my schedule rearranged itself and I took advantage of the opportunity to get in and troubleshoot.

I took apart the wheel and brake and got the hub bearing assembly out easily enough.

I noticed that the ABS sensor plug has a clever two-piece collar to attach it to the sensor. The outer cage portion of it did not seem to be fastened properly.

Also the bearing appeared to have suffered an internal failure, and was pumping blue grease out through the sensor area. Probably not supposed to be that way.

So I decided that the most likely occurrence was that my mechanic had installed a lousy part that was now failing after barely 5,000 miles on the car.

I went down to Toyota, bought a new bearing hub (with Aisin stamping, without blue goop trail) and spent half an hour putting it on the car.

Then I used the Autel dongle and app to clear the codes, and the test drive was smooth as butter. I'll need to drive it a bit more to be sure, but I really think this was a counterfeit part.

I'm giving Autel thumbs up for quickly pointing me towards the problem and making it easy to clear the ABS/traction control codes.

(general picture, no particular detail to show)​

This is the thing I randomly found that suggested wheel speed sensor played into the auto headlight control via yaw data.

We still have warranty coverage for the emissions system (including major hybrid components) in our USA car, but much of the car was only covered for two years.

 

The beams surely don't, but they've used some kind of clever logic to help the thing decide whether it is seeing oncoming automobile headlights vs. other light sources.

I consider it to be "good automation" because it usually makes the same choice I would've, and it is usually faster-acting than I would have been.

I'll have to see if the Autel system lets me do that wheel speed check. Thanks for the pointer!