Brakes failure

oh good, now hopefully that's that

 

Got to the train station to go home today, turned on the car up, and the ABS and the Brake lights were on. Drove home, and checked the DTC. Got C1364. unfortunately, my Auto Enginuity does not read the INFO codes, of which there are 21. I reset the DTC, and after pressing on the brakes, it did not return. I'll keep my fingers crossed and see what happens tomorrow.

 

AM Update, C1364 is back. I guess my weekend plans will change.

 

DTC C1364 is a malfunction of a wheel cylinder sensor in the brake actuator. The suspect parts include the brake actuator, the skid control ECU and the associated wiring harness.

Seems like you have a very obscure problem, if you can figure it out you'll be creating new group knowledge.

 

Patrick:
Just wish I could read the info code. I've fixed a few other obscure problems before. Maybe I'll get lucky again. Unfortunately, I don't have a warranty to fall back on. My first thought was that water got into something because of all the rain we have been having here.

 

I would call this a very appropriate thread resurrection! It's the same issue! Yay!

:thumb:

 

If your car had been in a front-end accident in the past, then I would check the wiring harness where it connects to the brake actuator, mounted to the firewall. Otherwise, I'd probably start by replacing the skid control ECU with a salvage unit, since that is much easier to do than replacing the brake actuator.

 

Patrick:
I think you hit the nail on the head. If I remember correctly, the connector to the actuator had the outer shell cracked when I rebuilt the car. It has been running fine for the last 18 months, but it could be a latent failure. That will be the first place I look.

 

Well, I got home for work early today, so I first looked at the actuator connector, and made sure it was properly seated. Then I hooked up the AutoEnginuity again, and reset the C1264. I powered the Prius down and up, and it came right back. I reset it again, and powered on and off 6 times, and it did not recurr. I had dinner, and after dinner, I powered the Prius up again, still no codes. I checked the AutoEnginuity to see what capbailities it has for the brake system, and I found the following available:
Test Mode (Z, G and Yaw Calibration)
Air Bleed
Reset Memory
Signal Check
ECB Utility

A pretty comprehensive list.
When the problem recurrs, I will run the signal check and the ECB Utility, and see if I can narrow down the problem.
Another thought, is that I might have to bleed the brakes. When I repaired the car, I found the hose from the brake fluid resevoir to the actuator disconnected. I reconnected it, and refilled the resevoir. It worked fine until now, so I never bled the brakes. I don't see how it could have had an air bubble all this time, and it now first complains.

 

As you powered up the car repeatedly, did you actually drive it? Perhaps you have to exercise the brakes, before the DTC will be logged.

 

No, just stepped on the brakes. However, each time it happened before, it happened as soon as the car was powered up. I'll acutally drive it in the morning. I will take the AutoEnginuity with me, so I can check it out right away.

 

The car has been fine all day today. Made several short trips, and a 100 mile round trip. Suspect moisture go into a connector somewhere, probably on the actuator.
The weather prediction is for a rainy week here again starting on Monday, so we will see if it happens again, or is gone for a while. When it returns, I will update this thread.

 

Well, it happened again today. C1364 and C1365. We had a lot of rain again today. That kind of clinches it, water is getting in somewhere! Also, it behaves differently now. Maybe becuase of the C1365. The brakes barely work at all. And regen is not normal. There doesn't seem to be any regen braking. We will have rain here all week, so I guess it will take a long time to dry out.

 

I suggest that you confirm that the brake failure symptoms are still present. Then disconnect the 12V battery to avoid logging further DTC and remove the cowl so that you can access the brake pressure actuator.

Remove the wiring harness connector, use a heat gun or hair dryer to completely dry the connector and the actuator terminals, then put back together to see if the brakes work OK.

If yes, then you have confirmed that connector is the problem and you now have to figure out how to weatherproof that part.

 

Patrick:
I agree with your approach, it is just what I was thinking of. What happened next has me more concerned then the initial problem. The ABS & brake light was on again this AM. When this happens, an alarm sounds, and the brakes barely function. I took the car on my normal commute, 2 miles to the train station, and back in the evening. The alarm was on the whole time. I took my Enginuity and read the codes & reset them. The car went back to normal immediately. I then took a 15 mile drive, it is still OK. My concern, is why does the system stay in that mode when it could easily restor normal operation? Maybe it should leave the lights on, so you take it in for service, but it should give you back normal braking. Obviously, the initial condition that caused it was gone.

 

A very good question.

My guess is that the design contemplates the possibility of an intermittent brake system problem. Once a skid control ECU DTC has been logged, if the audible alarm remains on and the brake system obviously is impaired, hopefully that would encourage the owner to seek Toyota dealer service as an immediate priority.

If brake system performance is restored then Prius repair may be placed on the lower priority list, as one of many tasks to do when the owner "gets around to it."

 

They could leave the alarm on, but killing the power brake boost when it will work is also dangerous. Leaving the alarm on itself would get must people to the dealer rather rapidly, it is quite annoying.

 

To resurrect this very old thread, I just replaced my ABS module and encountered the same error codes that the original poster did. I figured the used accumulator I installed was faulty, but then re-read this thread and caught the idea that moisture could play a part. Throughout the manual's instructions on replacing the ABS module, it suggested washing off any spilled brake fluid (which is plentiful throughout the process), and I recalled hosing down the bowels of the engine compartment at the end of the process. So today I booted up Techstream, erased the error codes (several times) and it now seems to be working much better. So, here's hoping!