A car is a machine that someone put together and made work. It can be fixed. When I encounter a problem, I pull the code(s) and research possible fixes by matching my symptoms with what others have experienced. I've fixed a lot of very expensive issues this way and for cheap. (I am comfortable going to the junkyard and picking parts.) I realize everyone has a different approach but I get results with my cars and that gives me confidence. True, Hydro-boost and integrated ABS/MC block is more complicated but it is a machine and can be fixed.

Reviewing this thread, we have 11 pages of posts, an unhappy camper, and no resolution. Why? We didn't get codes until late. When we did, we made progress. We didn't get accurate description of symptoms which would have facilitated diagnosis. For example squishy pedal with action at bottom and poor stopping power matches leaky master cylinder. FIX THAT FIRST. Address known and fixable issues first. You will be surprised how many cascading codes disappear when the root cause is fixed.

Here is a quick video showing the poor car.

I tried again to mimic the 'short' in the green relay by connecting sockets 1 and 2 of the relay leads (ABS sol relay removed). I had the key in the ignition on position for 1/2 hour.... no alarm at all.

I think the short can only occur if a solenoid is energized (active). The activation of one or several of the 13 solenoids/ valves can ony be initiated by the skid control ECU ... and the control circuit of the green relay can only be initiated by the skid control ECU.

So the short in the relay does not trigger the alarm (EVENT 2) .

The EVENT 1 can easily be demontrated. You see how the alarm is triggered by pressing the pedal various times and how the alarm is cancelled after pressure is back.

I hope you can see the video here
Shared album - Martin Werminghausen - Google Photos

Martin

Hi Sam,

Agreed on the squishy brake and the brake alarm EVENT1 ... that is (hopefully) a mechanical/hydraulic failure. I am confident that I'll find/fix that problem.

The confusing part is EVENT2 that came in very late. Sorry that I am not very experienced with the modern cars and OBD diagnosis.

So what is the root cause AND fix of alarm/codes EVENT2 (ABS Sol-relay circuit) ?
Do you think that alarm is going away with fixing EVENT1

Yes, it seems to happen under fuse boxes where the wire is crimped onto the female connector. You can't see it from above.

As for the thoughts, you really can't tell what the system is doing for checks and balances. If the computer sends a signal to turn on a relay but doesn't see the correct signal back it will set things off, this can happen in milliseconds.. A completely removed relay may set one fault on the computer where an intermittent one may do something totally different. Intermittent brakes is worse than none in my opinion. Some of these systems are sensitive enough to tell there's the improper current draw. I'll see if I can hunt down a good video with what I mean.

Here's one on a GM, about 9 mins in. The green crusties can corrode any wire that becomes exposed.
'14 GMC Yukon XL - No Communication With Inspection Computer - YouTube

This one a bit under 17 in.
Intermittent Stalling Ford F-250 : The Real Fix - YouTube

This one 22 mins in for a different type of connector but you get the idea.
Intermittent Stalling Ford F-250 : The Real Fix - YouTube

Thanks Mike.

I have seen the first crusty video.
I understand that there is a problem if corrosion is eating up the wire/connection and finally the connection is too tiny for current to flow. As a result the connection is disturbed- it is simply not enough.

Now I see the opposite with my relays ... I have a connection (short) that should not be there.... meaning I have too much connectivity and this 'too much' might cause the issue.

I don't know if the crusties might can cause a too much of a connection.

I still don't know what my first two codes want to tell me I should do and so far no one offered wisdom here, except for the advise changing the relays- because they can get stuck close-. And I changed the 3 ABS related relays
A) new relays don't change the picture. I still get these random ABS/ TRC alarms. After I cancel the alarm it comes back within 10 -20 miles.... super annoying.
B) The first two alarm codes seem to mention a short and the ABS sol relay. However if I am mimicking a short in the relay circuit (ABS sol relay) there is no alarm.

What do you think?

Martin

Too bad a Toyota engineer familiar with the braking system isn't on the website to chime in!

Until that angel Toyota engineer shows up I am renovating my leaking V8 valve cover gaskets. This is for gaining some time and ponder more about the brakes... waiting for some brake through.


Martin

At the junkyard this morning, I was tempted to pull an abs/mc module and take it apart. They can be found in early 2000's Lexus GS, Lexus SC, Prius, and probably others. This one was in a beat up 2001 GS300.

Hi Sam,
thanks for helping me (and others, hopefully).
I was thinking to bite the bullet of a new unit (1.4K) and then renovate the unit I am pulling.
At least in this case: If it does not solve the unexplainable ABS alarm (EVENT2) and I am having the same issues... then at least I know that the old unit is not involved at all.
However EVENT1 (squishy brake and the brake alarm after stepping on the brake 5/6 times) should be solved with a new unit.

Martin

update brakes
A)
I was reading the codes again today:

1) C0287 open/short circuit in ABS Solenoid Relay Circuit
2) C1223 malfunction in ABS Control System

These seem to be codes from EVENT2 (the code that cannot be canceled unless I pull the relay/

You guys were sometimes talking about the route cause for the codes, meaning there is the main problem and then the electronics follow up and there are more codes.
If I see these two codes... then the root cause might be the following:
There is a problem in the ABS Control System (malfunction in the skid control ECU causing Code C1223??) That is triggering the alarm.... and then I pull the ABS Solenoid Ralay and get rid of the alarm but I am triggering the second code C0287....
Can it be that simply pulling the ABS sol relay will trigger C0287?

Could anyone of you guys check this?

What happens when you simply pull the green relay....any ABS code showing?


I ordered another used Skid control ECU when is a good time to install this one?
Should I install this ECU first before the hydro booster swap in order to see if this will solve the ABS codes?



B) Then I started digging up the fuse box in order to search for crusties (see pictures) . The fuse box seems to have a closed bottom, other than the US cars.
There are 4 access points to the box.
1) front right: battery plus
2) rear right : ground (?)
3) rear left : biggest harness coming from fire wall
4) front left : harness to the front

The 2 harnesses don't seem to be connected to the box with plugs... but the harnesses go straight in.. making it difficult to remove. I think I leave the crusties there.

I will clean up the ground connections as much as I can and assemble everything back.

C) I ordered the new hydro booster unit. I simply wanted to start with a clean slate after removing the old booster several times now and no progres.

Now the question is if I should work in a certain sequence in order to still catch the cause of the problem.

Sam said fix the master cylinder first.
I was thinking maybe I should swap the ECU first and see if anything changes?


best, Martin

Attached Images

           

Update2
I disconnected the battery (for cleaning all the ground connections that I saw and the battery terminals.
After reinstalling everything I tried to cancel the 2 ABS codes and it worked this time.

I can hear the brake motor running for a very long time each time put the key into ignition.
That really mean that pressure storage is loosing pressure rather fast.
I'll take care of this and replace the hydro booster first, I think.

Best Martin

ps I am sorry that this is so lengthy, I wished the problem solving was faster.

This Toyota owner has the same C0278 and C1223:

VSC, TRAC OFF, ABS, & BRAKE - Code: C0278 & C1223 | Toyota Nation Forum

Some suspected ECU and suggested checking grounds. I see one of your photos has a ground strap disconnected.

Pending resolution of electrical issue, changing accumulator is a good idea. Did you look into mc swap?

Actually this topic has more info on the ABS booster/master cylinder than any other topic I've seen on this forum, it will help many others in the future.

And I maybe the first, it's ironic that I've been following this topic, in the last 2 days my brakes are starting to go bad, after my T4R sitting all night as soon as I turn on the ignition and I get the alarm, brake light as well as the other 3 lights and my brake pedal is hard as a rock, I can barely get it to not roll when I put it in gear if I press hard enough, apparently the pressure has escaped/leaked down, after about 3 to 4 minutes of just having the ignition on the pressure gets build up enough and the alarm and lights go off and the pedal is back to normal.

So far I'm only having this issue after overnight, 6 to 8 hours is sitting no problem.

I pretty sure it's the electric motor, and or the accumulator, but could also be the pump

I think I'm just going to get the entire ABS booster assembly and just get it done.

I may be back asking for advice, or giving it if I can as I go about replacing it, etc.

I will be ordering parts his weekend.

Au, send your "core" brake assembly to Werm! Hard pedal is non-boosted braking with good master cylinder. I concur with accumulator diagnosis. Werm has soft pedal that goes to the floor. That means his boost is working but the pressure is not getting to the calipers. Werm needs good master cylinder and good ABS control module.

To give you guys something to look forward to, I stomped on my brakes today and really enjoyed them. Nice medium effort pedal with good modulation and plenty of stopping power. I have a Limited which has 13.2 inch rotors. 12.6 inch is standard spec.