Brake pedal vibration on startup

[lininjim]

Hi all, I've done a bit of searching but I can't seem to find if anyone has experienced this.
We have a UK 2004 Prius, we've had it from new, still only about 25,000 miles. For the past month or so when I have been starting the car in the morning there have been a number of warning lights come on including a big triangle with a ! in the middle and at the same time the brake pedal vibrates (quite violently) under my foot. It clears the warnings then and there's no further vibration.
It started only happening in the morning but it has gotten worse.
In my mind I thing the braking is not what it was but that is purely subjective.
I dropped it into my local dealership on Wednesday (we have extended 5 year warranty - whew) for them to check out yesterday morning.
When we called they said they could find no fault and no codes logged in the computer.
I told them I didn't want the car back till they had sorted it as it ws (in my mind) a safety hazard.
Today I spoke to the manager who said that he thought he had felt the vibration for himself but they had no idea what it could be.

Soooo, does anyone here have any idea of what this might be, or have had it yourselves?

Thank you for reading my rather long posting.

Cheers from England!

[qbee42]

My first guess would be the brake accumulator pump, or whatever you care to call the electric boost pump for the power brakes.

Tom

[lininjim]

Thanks Tom, any feedback I get on here tonight I'll take with me tomorrow.
I appreciate the reply.

Jim

[Bob64]

Perhaps its the pump that gives feedback to the brake pedal cylinder (if there is one, as I may be making parts up)?

[Patrick Wong]

Originally Posted by lininjim

...We have a UK 2004 Prius, we've had it from new, still only about 25,000 miles. For the past month or so when I have been starting the car in the morning there have been a number of warning lights come on including a big triangle with a ! in the middle and at the same time the brake pedal vibrates (quite violently) under my foot. It clears the warnings then and there's no further vibration...When we called they said they could find no fault and no codes logged in the computer.
I told them I didn't want the car back till they had sorted it as it ws (in my mind) a safety hazard.
Today I spoke to the manager who said that he thought he had felt the vibration for himself but they had no idea what it could be.

A very interesting problem. Since the service manager experienced the vibration himself, hopefully he acknowledges this is a real problem. Has the problem been escalated to Toyota GB for help?

I took a look at the diagnostics section of the repair manual, studying the schematic diagram that shows how the various brake parts relate to each other, trying to figure out how pressure from the brake pressure accumulator pump might be transmitted back through the brake master cylinder so that you would feel vibration in the brake pedal. There are two "master cut" solenoids that control flow of brake fluid from the brake master cylinder. Maybe one of those solenoids is open momentarily when you are starting up, which allows you to feel the vibration.

DTC C1315 or DTC C1316 are supposed to be triggered if there is a problem with these parts; but since the problem is intermittent, maybe the diagnostics are not sensitive enough to trigger.

If a solenoid is the problem, the fix would be to replace the brake actuator assembly that contains the various solenoids. I am very interested to hear what the resolution to your problem is.

[lininjim]

So far no response from Toyota at all.
It didn't do it when I collected the car (of course) and we didn't use it on Sunday. On Monday it did it 4 times, I captured the warning lights on my digital camera and it did it again this morning, it did not do it at lunchtime!
Photo attached here (of the lights coming on)
I will post back and Patrick that's great information thank you.
Cheers Bob, I don't know lol

[Patrick Wong]

Originally Posted by lininjim

...On Monday it did it 4 times, I captured the warning lights on my digital camera and it did it again this morning, it did not do it at lunchtime!
Can I attach a photo here (of the lights coming on)?

Yes, please attach your photo. Note that attaching a file is a choice within "Additional Options", while you are composing your reply.

[lininjim]

there you go, sorry about the quality, it's a screencapture of a mov file taken on my camera

[Patrick Wong]

Sorry, I can't identify the warning lights in your photo besides the master warning light (red triangle) and the air bag light. Since the air bag system is unrelated to the braking system, I am wondering if your problem is just a bad 12V auxiliary battery. Have you replaced the original equipment battery yet; if not maybe this would be a good idea.

Can you please identify the other warning lights that came on and list them?

[lininjim]

They are the low temperature warning (snowflake).
A car skidding, VSC, ABS, (!), airbag and the /!\
---

They all come on apart from the /!\ for say 1/2 sec, then the /!\ comes on for a further 1/2 second then they all go out apart from the airbag for a final 1/2 second then they all clear. They have always come on like this apart from the /!\ symbol.
Oh and when it is on is when the brake pedal vibrates.
Does that help at all?
I've attached the video clip, might be clearer?
.mov file zipped.

also still on original battery