Warning lights but can't figure out the root cause

I drove my 2005 Prius 2 hours and parked it for 5 hours. No problems on the trip down. I got back in it and it started up just fine. I was sitting in the parking lot with my foot on the brake (hadn't moved yet) and the following occurred:

The brake pedal seemed to push back on my foot
The red exclamation point illuminated
The yellow exclamation point illuminated
The ABS light illuminated
The VSC light illuminated
The red parking brake light illuminated (not shown)

All of these lights point to the skid ECU. It seems like my skid ECU is toast or something called the ABS & BA & TRAC & VSC Actuator is an issue (never heard of it but I see it connected to the skid ECU). I did a visual check of what I could and everything seemed in order. I pulled a bunch of fuses and I didn't notice any that were blown. (I didn't pull them all but will tomorrow)

After not finding anything, I drove back home. As expected, I had no regen but the bigger problem was that I had no power assist on the brakes. A few times I actually did skid and the car brakes really bad without regen or power assist. If it was raining or snowing I could definitely see a hazardous situation.

I'm kind of at a loss here. Tomorrow I'll pull the kick panel down and see if the skid ECU is getting power but I can't think of anything else that would cause this situation. Any other ideas?

 

The car started and ran fine for about 45 seconds to 1 minute. I can't remember if I just put my foot on the brake or attempted to shift into drive when the problem happened. On my two hour trip back home I stopped a couple of times and everything was normal, except the issues I listed in my original post.

I'll have to check this in the morning. I normally hear it but I didn't take notice to it today.

I have zero codes. That was the first thing I checked, which is why I'm really confused. I would have thought for sure that one or more of those fault lights would create a fault code.

I don't know how the communications work on the Prius but I do similar work in my career field. Just a guess but if the other ECU's don't poll the skid ECU and the skid ECU fails completely, there will be no way to set a code. If the other ECU's look for data or some sort of heartbeat signal then one of the other ECU's should have reported a failure.

Like I said, no codes and the 12V battery appears to be working just fine.

 

I have a Scangauge II. It seems to be functioning just fine as everything is operational on it. It reported a DTC last week for the catalytic converter. Maybe it can no longer read the DTC's, not sure yet.

 

I understand that but I'm not going to discard it. Anyhow, I've been working on a CAN diagnostic tool for use with a computer on the Gen II Prius. It wasn't ready for testing on the car yet and certainly not in this situation but I'm going to try it out today. I'll be checking my car in a few minutes and hopefully I can locate the problem.

 

The skid ECU isn't toast. The light for the traction control doesn't light until I unplug one of the connectors on the ECU.

Whatever the normal noise is when you step on the brake before you start the car isn't normal anymore. IIRC, it lasted for a second or so normally. Now it clicks for less than 250mS. Not sure how to explain it but the noise isn't normal at all. I checked the master cylinder and it's at a normal level.

Here are my questions:

1. I know the noise emitted when you first step on the brake has to do with the brakes but what is it?

2. Is there something electronic on the master cylinder I can check?

3. When I press on the brake, there isn't any resistance until the pads/shoes are hitting the wheel. Would a defective master cylinder cause this type of problem? It kind of makes sense because the problem occurred with my foot resting on the brake and I hadn't moved the car yet.

I'm not very knowledgeable on brakes so if there are any checks I can do that anyone can think of, please let me know. Bringing my car to the dealer is not an option.

EDIT: Would the brake master stroke simulator cylinder assembly or the brake control power supply cause this type of problem?

 

Some more info if this helps anyone.

I'm able to get that noise when you first step on the brake back to normal. I can do this by removing the ABS 2 relay. This is an assumption but it seems as if the master stroke assembly might be okay since it's connected to the ABS 1 relay. It seems as if the ABS & BA & TRAC & VSC Actuator could be an issue since the ABS 2 relay goes to it.

Other pertinent information:

The fail signal from the brake control power supply will go from ~1VDC to ~12VDC every 250mS. Not sure if this is normal or not but it was just an observation. All other signals appeared to be okay.

The other strange thing is that it literally feels like I have no brake fluid. When I release the brake pedal it sounds like there is a vacuum coming from the brake pedal area. I can verify it's there but again, not sure if this is normal if the electrical portion of the braking system is inoperative.

 

Because I can't afford it until Monday.

That's a little dramatic.

Great information, thanks. Is there a full list of codes? I can view data on the CAN. Is there anything there that's useful to diagnose this problem?

 

Thanks for the help Vincent. First thing in the morning I'm going to try this and hopefully it gives me some useful information.

 

Yup, it's for a Gen II. I was confused about the comment regarding the CAN because of this: