ABS Module Failure After 17V718000 Recall

I think it’s unlikely that the recall repair caused the later failure of the skid control ECU. The recall identified by NHTSA as 17V718000 is called campaign H0R by Toyota, whose Technical Instructions for Safety Recall H0R (PDF) don’t describe any work being done on or near the brake system, which has no components near the fuse. The only under-hood tasks (pages 13–14) are to remove the inverter cover, check for voltage, and reinstall the cover.

As for the repair cost, the skid control ECU is sold only as part of the brake booster with master cylinder assembly, part number 47050-47210, list price $698.01. One edition of Toyota’s Flat Rate Manual allows 2.1 labor hours for replacing it (operation number 461101, ZVW35 series).

 

Is anybody collecting those skid ECUs and taking them apart?

I'm really curious exactly what is going in there that ends up slaving the hazards to the SP1 pulse (which really sounds to me like what is effectively happening).

And is the behavior really the hazards? That is, both turn signal (amber) bulbs in front, both turn signal (amber) bulbs in the rear, and both directional arrows in the combination meter? That puzzles me even more, because, does the skid ECU even control those? The wiring diagram shows them as the responsibility of the Turn Signal Flasher Assembly (no surprise there), which is activated by a simple yellow wire to the Hazard Switch, which grounds it.

Hmm ... oh, but wait. That hazard switch is wired to pin 14 of junction block no. 3, connector 3A.



It leaves from 3A pin 38 and continues as a yellow wire to the flasher.

But hey, those two pins are in a group of four in that junction:



Where does 3A pin 63 go? That's another yellow wire, and lands at the Body ECU connector L7, pin 3. I suspect that is so the Body ECU can do the flashy-flashies when it locks and unlocks doors or the alarm goes off. It can just pull that circuit down to ground, and it's the same as pressing the flasher switch.

That leaves 3B pin 4. Where does that go?

Bingo, as a sky-blue wire to pin 10 at the Skid ECU.



So what, exactly, is the Skid ECU doing with this hazard switch signal?

The mnemonic HZRI sort of suggests it's an input—does the skid ECU have any reason to want to know when you have activated the hazards?

Or, is there any known reason (other than when it goes flaky) why this would be an output, and the Skid ECU would want to activate the hazards?

I wonder what would happen if a person just ... forgot ... to connect that wire at pin 10 of the Skid ECU.

Or, if it's supposed to be an input, maybe just added a diode, so the hazards wouldn't be activated if that "input" started getting pulsed to ground.

Where it goes through connector AL2 at pin 16 might be a more convenient place to intercept it ... well, except it looks hard to reach with the dash top on. Ugh.

 

The very last item Techstream shows in my Skid ECU Data List is "Hazard Switch History". Mine shows "Incomplete."

Somebody tell me this isn't some kinda vestigial, not-even-used feature that is causing so many people these headaches when it goes haywire and starts acting like an output?

 

is the 'hybrid propulsion recal' the ipm module? i have been reluctant to take mine in because of all the horror stories.
how many miles on yours?

 

There have been various other reports on PriusChat of people's brake ECUs going bad in this annoying way where they flash the hazards at a speed-dependent rate. It's a weird brake ECU thing. The hybrid propulsion recalls don't touch the brake ECU, as Elektroingenieur pointed out in #2, and the other reports of this goofy brake ECU thing have not indicated any such connection. If you're avoiding a recall because of "horror stories", at least there's no need to propagate a one-off coincidence as a new "horror story".

 

More than a month after locating the HZRI signal at pin 10 on the brake ECU, Chap finally asks himself, "say, what pin does the wiring diagram say the SP1 speed pulse comes out on?"

That's pin 11.



So they're right next to each other, there on the top row, in a weather-exposed connector out there under the hood.

I wonder how many cases where the "ECU goes bad" in this way, it isn't some spider setting up house between those two pins (radiant!), or a tin whisker or malachite growing between them.

I think the hazards are activated by pulling down, and they can be activated with the car off, so that must normally be pulled high all the time.

In most of my experience with malachite growing on connector pins, it seems to be the ones with 24✕7 +12V applied that grow it the fastest.

 

I am a new member and this is my first post, so please forgive any etiquette clumsiness, but do let me know so I can learn.

I started experiencing this exact problem one week ago. In particular, the hazards started going on intermittently whether the Prius was powered on or not. Attempting to drive caused what I assume to be the hazard/directional relay under the dash to increase in frequency proportional to my speed. My regular mechanic was at a loss and said I should take it to the dealer which I am loathe to do as the car is past the ABS extended warrantee and I don't have a spare $3,000 lying around.

Since last week, the problem has gradually become constant. So that I can use the car in a limited way, I pulled the hazard/directional fuse and have been using hand signals. Occasionally, I would get check lights (Skid, Brake, and ABS) with the expected loss of braking assist. Whenever I put the fuse back, the hazards go on.

As a software engineer (with some hardware background), my instincts suggested this was caused by a short, so I was thrilled to see the excellent analysis by ChapmanF. I intend to troubleshoot this problem, hopefully for the benefit of all unfortunate owners such as myself who have this problem.

Toward that end, I started by getting a BlueDriver OBD2 scanner which reports the following error codes:
* Antilock Brake System: C0210 (?), C0215 (?), and C1238 (Foreign object attached on tip of rear speed sensor RH)
* Entry and Start: U0155 (Lost communication with IPC control module)
* Power Source Control: B2282 (Status: CURRENT/HISTORY - vehicle speed signal)
(Underwhelmed by the output, I will likely return the scanner and figure out how to use Techstream at some point).

Since the weather is nice here in eastern MA, I am now going to remove the wiper assemblies, disconnect the harness from the skid ECU, and look for corrosion and/or low resistance between pins 10 and 11, on both the harness connector and the ECU plug.

Any other suggestions on what I should do while I'm in there would be much appreciated!

 

This isn't the sort of issue that I would expect any specific trouble code to exist for (some engineer would have had to be thinking "hmm, what code should I use if some random short develops between two pins that happen to be the vehicle speed signal and the hazard switch?").

That said, I think I'd have to say a B2282 (the power management control ECU complaining that the vehicle speed signal pulse rate doesn't match the speed value it's getting from the brake ECU over CAN) seems really almost as good.

I think what you're proposing to check is pretty much what I would try first.

And if I didn't find anything obviously fixable from the outside, I might even see if I could open up that side of the actuator just to get the circuit board out and get a look at that. But, I might well start by trying to buy a cheap busted actuator assembly first and practice on it, to find out whether there is a way to open it and extract the board without damage.

I had the cowl off recently while playing with the EGR cooler, and I took a look at the access to that side of the actuator while it's in place, and it wasn't very inviting. But I'd be happy if there's a way to address this issue without disturbing all the hydraulic connections and hauling the whole thing out of there.

 

Thanks for the encouragement! Life got in the way, so it took me a few days to get to this. While I didn't find a smoking gun, using an idea mentioned earlier in the thread, I had a very acceptable outcome, nonetheless.

Visual inspection of the harness and ECU connectors showed both to be pristine AFAICT. While I couldn't see deep into harness holes, the corresponding pins on the ECU looked brand new, so it seems unlikely there was any corrosion inside the harness connector.

After making a couple of mistakes that I caught, I decided it would be prudent to document the testing I did with pictures which I've included. In all except for the one with test leads swapped, I connected the red(positive) terminal of the multimeter to the red wire with the dupont connector and the black(negative) terminal to the blue wire. The multimeter appears to use +100 mV for resistance testing, so I thought this would be reasonably safe for the ECU. Of course, both Prius batteries were disconnected for this testing and the hazard/directional fuse had been pulled.

Harness pins 10&11 came in at 1.3 M ohms:


ECU pins 10&11 came in at 88 k ohms...:


...and, when the test wires were swapped (off camera), 2.75 M ohms:


However, the ECU resistances were not constant. Both slowly increased, probably due to output capacitance charging up. In any case, no obvious shorts. (In hindsight, it might have been interesting to check resistance between each ECU pin and the corresponding power and ground).

Not wanting to put the car back together empty handed and being a "forgetful sort" , I thought I'd try the following suggestion:

With my trusty wire cutters, I snipped the sky blue wire going to Skid ECU pin 10 and put the hazard/directional fuse back in. The result is that I have full use of my 2010 Prius again including directionals and the hazard button!!!!! I've put only 50 miles on it, but everything is working beautifully for now. However, I wouldn't be surprised to get another ABS system code C1238 in the future as I can't see how Skid ECU pin 10 could be directly related.

So, why would the Skid ECU need to pulse the hazard lights in the first pace? A friend suggested that it's to get the attention of people behind you during really heavy breaking in an emergency. He said he saw this exact behavior during a race (stock car?) that was on TV.

Lastly, I quite agree that removing the ECU cover plate with the unit installed looked daunting with only three of the four screw heads reasonably available:


Also, I'd bet there's a gasket that might not survive the removal. However, such a gasket that has lost integrity could well be the source of the problem.

 

Thanks for the investigation!

I'm not at all sure the skid ECU does need to pulse the hazards. The mnemonic for that pin, HZRI, makes me think maybe it's intended as an input.

Oh, hey, I was looking in the wiring diagram before, which only has the mnemonics, but there's a "terminals of ECU" table in the Repair Manual also. Hadn't thought to look there before:



So I'm enough of a Toyota whisperer to have guessed "HZRI" right. Plus a couple bucks that ought to buy me a coffee. (The ECU does have the ability to pulse the brake lights in the rear; one of the other pins is an output to the so-called "stop light relay", which is really fancier than a relay, and has multiple inputs.)

Now I haven't got any better idea why the skid ECU needs a hazard switch input either. But you can pull this up in the Techstream data list:



I'm now feeling a sudden wave of insecurity, wondering if my hazard switch history is complete, or what I need to do to complete it.

So the thing is intended as an input, and clearly what's happening (when it does the speed-dependent blink thing) is it's just getting unintentionally bridged to the SP1 signal next to it. Somehow. And if you don't see it at the connectors, it's probably on the circuit board (and possibly something that has failed in silicon, but the only way to know will be to find out).

This is where my next step might be to shop around and see who is selling a Prius actuator assembly the cheapest that they don't even claim works, just to open up the ECU side, find out how it is gasketed, find out how difficult it is to extract the board, and so on.

If somebody has one that they took out of service because of this issue, that would be sort of ideal.

As to three of the four screw heads accessible, I wonder if a technique could be developed that would hang the thing from a strap for support, keep the hydraulic lines attached, unbolt it from the firewall, and see if there was enough motion available to get to the fourth screw. Even if a pain, it might be worthwhile if it saves futzing with the hydraulic system and the subsequent long-form bleeding.

I wonder what it takes to move that wire harness duct right next to it.

Knowing now that HZRI is an input, there would clearly be the option of putting a diode where you put your cutters, and you could then have non-blinky flashers and still preserve the completeness of your hazard switch history.

 

My pleasure! Thank you for your valuable insights into this problem.

A Toyota whisperer you are and a very good one at that! Happy to buy you a coffee anytime - please let me know how.

Agreed. Also, it could also be water contamination of the board. My son picked up a dead "high end" light saber for nothing which turned out to have signals bridged by the residue left after water contamination had dried. I just cleaned it up with a little alcohol and it was good to go.

Yes, this sounds promising. While I've worked on other cars I've owned, I stopped when I got the Prius figuring "Hey, it's a Toyota so it'll work forever!" OK, I wasn't really *that* naive, just somewhat naive, figuring I had a good 20 years. In any case, being a newbie at looking under the hood of my Prius, I wouldn't know where to begin to look for such a part. Any help would be appreciated. Alternatively, if you found one at a reasonable cost, I'd be happy to reimburse you for it.

Great idea! I think this has a high chance of success.

True enough.

Speaking of hazard switch history, I need to get TechStream up and running. For starters, is there a less expensive alternative to the $495 Mongoose Pro MFC 2/3 if I were to go the "company recommended" route and buy a 2 day "Professional Diagnostic" subscription for $65? Two days is *so* short, though.

I understand that there are other options using so-called cracked (and malware infested) versions of techstream, but this kind of thing makes me a bit nervous. Should I be?

Thank you again for all of your help!

 

Nah, that was a joke, in the old "that plus a couple bucks will buy you a coffee" vein (although, back in the day, it was more like "that plus fifty cents" or so).

There's always Googling for the part number to see what shows up, or searching for it on ebay. For this particular issue, it might be worth putting a WTB post in PriusChat's private sales forum, something like "have you replaced a Gen 3 brake actuator because of the hazard flashing issue? do you still have one you replaced?" Some members here run repair shops and might have one around.

If you want to go legit, you can go official on the software but use a less expensive dongle. I've had good results in Gen 3 with this one (about $170), and I've heard of successes with a VCX Nano sold by VXDiag, which I heard was around $80. The Mongoose Pro is the one Toyota has tested and stands behind, but after all, J2534 is supposed to be a standard.

I think the people who go that route tend to just dedicate an old beater Windows laptop to that use, turn off all its network connections, use it for nothing else, and avoid worrying too much. I can't think of any reports of rotten experiences that I've heard.

 

Once again, thank you so much for your help!

I haven't done anything on getting a broken actuator, yet, but I know it's in my future. However, the frequency of faults has gone *way* down. In the three weeks or so since my last post, I've gotten only one Skid/Brake/ABS check light AFAICR and that was soon after I posted. So, what could have changed to explain this? Thinking back, two possibilities come to mind.

First, the weather has gotten quite a bit cooler, going back to seasonal norms.

Second, when I did my initial troubleshooting and removed the cowling, there was a ton of composting leaves that I cleaned out. So much so, that I suspect it caused water to pool in the basin of the cowling. A few of the bolt heads near the bottom were quite rusted. At the time, I wondered if that could have caused water to drip on the skid ECU as the ECU cover and screws looked surprisingly corroded.

FYI, I have steadfastly ignored my mechanic's advice to ditch the plastic weather guards under the engine compartment which often get loose or, on one occasion, completely ripped off because it went under the LF wheel! That was a pricey part as I recall. :-(

I wanted to go legit, but the price was prohibitive. While I made good money when I bought the Prius new 12 years ago, that's not the case now. So, I've got to watch what I spend and want to keep the car going at minimal cost, if possible.

I had a beater laptop lying around, so I upgraded it to Windows 10, got my VCX Nano, installed the virus ridden software that came with it, and put it on it's own external Guest WiFi network as it seemed to need Internet access to get its own license. I've used it successfully to get some reports of the skid ECU check(s) that I mentioned which I've attached.

Not surprisingly, when I turned on the beater today, Windows 10 promptly detected the virus "Win32/Ymacco.AA88" in "Toyota Launcher.exe", the program supplied by VXDIAG to load in and patch Techstream 15.

Should I clear the ABS codes and, if so, how do I do that? Also, is it possible to save the ABS data before clearing it?

 

Looks like you've already got pretty complete printouts ... what more "saving" would be useful?

Those definitely are some interesting right rear wheel speeds there.

 

I wasn't sure if the printouts exposed all the information. Good to know that they do.

Yes, interesting RR wheel speed, indeed! What's not clear is whether the speed sensor is really bad or that this is yet another symptom of an already suspect skid ECU.

This post has a PNG with interesting skid ECU resistance checks that I'll probably do the next time I'm in there:

Error bleeding brake acculumator after replacement | PriusChat​

Guess I'm overdue to pay for access to the technical docs. Looks like some useful tests in there.

 

For anyone that discovers this thread and has the same problem - I tried the solution discussed by Lucy/Chapman. It worked perfectly (so far). I've driven around 300 Kms since without issue. If something comes up I'll come back to the thread.

 

Hi All - first post ever, Hi! I am experiencing the same issue in a gen III Prius. The car is new to me and I was wondering if there were instructions about how to access the baby blue wire that needs to be snipped? TIA!!

 

Also, mine is not a plug-in, is this fix still appropriate?

 

My prius is not a plug-in, had the same issue and the suggested fix worked out well, especially compared with the ~$3,000 for replacing the ABS system quoted at the dealer. I also passed the state inspection 1 day later.

Here is what I found helpful (as a complete novice at any sort of mechanical work):

1. There is a youtube video which shows exactly where the wire is. It's helpful for connecting the visual under the hood to the diagrams above. I can't post the link because I'm new to the forum, but it's called "toyota prius hazard lamp flash fix without change abs control unit".

2. To access the skid ECU, you need to remove the two wiper cowls (plastic and metal). If you have the right tools (socket wrench and ratchet), it's easy. There is also a video, "How to Remove Lower Metal Cowl Cover 10-15 Toyota Prius", on youtube showing the steps