Brake Booster ECU Woes: How do I Reset the ECU?

I accepted delivery of a new 2015 Aqua (Prius-C outside Japan) recently. Using a DENSO "DST-i" OBD Scan Tool (with the newest firmware as of March 2015 firmware) and of course with Ignition ON, I sent a "Stop Brake Control" command to the vehicle, which communicates with the Brake Booster Assembly. I later exited from that "Stop Brake Control" mode, and then I performed the required 120-second "Brake System Initialization." After that I exited out from the DENSO Scan Tool, I noticed that 3 or 4 dash check lights were lit. Normally the brake system "Initialize" command via the DST-i should address and clear error flags (check lights), but in this case it did not. I used the DST-i again to Reset, the pertinent flags were not clear as evidenced by the fact the check lights remained lit.

Not knowing what to do, I returned to the Toyota dealer with the car and consulted about solutions. They changed the brake fluid to see if that would help, resulting in 1 of the check lamps no longer glowing (that flag was somehow cleared). But brake fluid replacement procedure unfortunately did not clear the remaining check lights.

Since the DST-i is an official DENSO scan tool used in the proper manner, this kind of problem should not have happened. But since the dealer changed the brake fluid thinking that would solve the problem, and since it did not solve the problem, the dealer had no further explanation, so they simply said it would cost approximately $2000 (equivalent) to replace the entire Brake Booster ECU. And since that part is not normally stocked, it will take time to order and receive it.

A DENSO scan tool is technically not a Toyota problem, but DENSO is inseparably tied to Toyota insofar as Toyota uses DENSO scan tools. To even change the brake fluid the dealer must use the DENSO scan tool to issue the "Stop Brake Control" command. But of course, since it was me who sent the command with my own DENSO tool instead of the dealer doing it, the dealer will of course not take responsibility to investigate the matter too extensively, opting instead to say that a complete replacement of the Brake Boost ECU is the only recourse.

Clearly, there is some kind of design problem in the Aqua / Prius-C Brake Booster ECU to even allow this kind of problem to occur. Nevertheless, I wish to keep the focus of this post on what can be done to solve the problem.

Simply put, I am sharing this experience in part to warn others about issuing DST-i commands to the Brake Booster on the Aqua / Prius-C but also in part to ask your advice and help. Do any of you know of the Brake Booster ECU stores flags in its own flash memory? Surely there must be a way (other than just replacing the ECU unit outright) to clear flags in the Brake Booster ECU. The vehicle drives fine and the brakes work as usual. The only "problem" is that the ERROR FLAGS remain perpetually lit.

How could I possibly clear the Brake Booster ECU, other than simply removing battery power?
(Removing battery power won't help of flags are stored in flash memory.)

Thank you.

 

Thank you for your reply.

I disconnected the battery for more than 15 minutes. Upon reconnect I confirmed the check lights are still lit. So as I expected, there is flash memory in the ECU which saves these flags. Flash memory will not be cleared by removing power.

Here are photos of the dash Check Lamps I mentioned in my opening post. Sorry, but because I am new to this forum, I am technically not allowed to post URLs, so you need to manually enter them in your browser:

http://bit.ly/1EwpUvF

http://bit.ly/1PLWt4M

http://bit.ly/1etwvlV

Further thoughts and advice would be greatly appreciated.

Thank you.

 

Thank you again for your reply.

The DST-i scan tool (& TaSCAN) and the Global Techstream (GTS) software are basically the same, except that the GTS is the software edition running on a PC while the DST-i is a standalone unit with built-in screen. HOWEVER...

I am pleased to report that the problem is now fixed. An engineer friend has access to Toyota's TECHINFO website which provided the solution:

1) CLEAR CODES: With Ignition (IG) OFF, connect OBD pin-13 (TC - Timing Check) to pin-4 (pin-4 is GROUND) — manually short them together and leave them shorted together. (I used an OBD connector with wires exiting the back to accomplish this.) Then switch on IG and press the foot brake more than 8 times within 5 seconds. Now disconnect pins 13 & 4.

2) CLEAR CALIBRATION DATA: With IG OFF, steering wheel centered, gear in P (park), foot brake not pressed, and Parking Brake not set, switch IG ON. Connect OBD pin-13 (TC - Timing Check) to pin-4 (pin-4 is GROUND) briefly and repeatedly four times (or more) within 8 seconds.

3) INITIALIZE & CALIBRATE: With IG OFF, steering wheel centered, gear in P (park), foot brake not pressed, and Parking Brake not set, connect Pin-12 (TS) to Pin-4 (GND) — manually short them together and leave them shorted together. Turn IG ON. Wait until the initialization sequence is done (you will hear solenoid noises and see dash warning lights flash), which takes about 2 minutes. Turn IG OFF. Disconnect pins 12 & 4. I then used the DST-i scan tool to verify all was well.

So there appears to be a bug at work. Performing a software CLEAR & INIT using the DST-i did not work properly (the dash check/warning lights never were cleared). But doing the same thing via the car's built-in RESET and INIT/CAL works perfectly.

I hope this information helps others.

 

Perhaps they did know the solution but preferred to avoid mentioning that so as to profit off a Brake Booster sale. Dealers do make most of their money selling us "options."

 

The warning lights pertain to the braking system, so that explains why they make you jump through hoops to clear them.

Toyota is nuts about liability. Here in Japan they build in TV capability to all navigation systems they sell, but the TV features (any video features, actually) are disabled until you stop the vehicle, put it in Park and set the parking brake! Most people here avoid the factory navi option for that reason, going to their local AutoBacs and putting in a 3rd party navi unit instead which lets you show as much video as you want while blazing down the highway. It's silly you cannot show video while you drive seeing that the person most likely wanting to watch it is your passenger. I can't imagine ever wanting to watch video myself as a driver. Then again, I cannot comprehend the mentality of people who text while they drive. When I drive, I DRIVE. That's it.

Anyway, I hope the info in this thread can help some of you.

 

Thank you for sharing your experience, Matt. I appreciate hearing your thoughts and recommendations.

I am aware of G-scan, which is represented here in Japan by this company:


株式会社 インターサポート


But I am curious about your comments regarding DENSO scan tools. DENSO is a separate company from Toyota, but here in Japan the two firms are so tightly intertwined they appear as if they were the same company. As far as I know, DENSO tools are the factory-grade tools insofar as Toyota dealers in Japan use them. I would guess that one would not need them at the assembly "factory," but I lack information on that.

Although I have found a couple "bugs" in DENSO scan tools (such as triggering of Warning lights mentioned in this thread, and accidental triggering of high-current draw on Noah, Voxy and Esquire vehicles even after you disconnect the scan tool), it's still difficult for me to imagine that a third-party aftermarket scan tool maker would best DENSO in its understanding of Toyota vehicles. G-SCAN is much snappier to use than DENSO scan tools, that's for sure. DENSO scan tools are dog slow. But is "compatibility" really "better" across the full spectrum of Toyota cars manufactured and sold here in Japan? Again, I have my doubts. But I would agree that after-sale SUPPORT would be better with anyone than DENSO. With DENSO, you buy the tool and that's it. Go ahead and report a problem, but you're stuck until they get around fixing it. In that regard, you may be right about G-SCAN being better.

As to Navi systems here in Japan, Japanese dealers will not "flip it on" even if you ask. Boy, I wish they would. But they are so hard-headedly stubborn and serious about liability they would never even in their wildest dreams consider it. That's why most Toyota buyers here ditch the dealer option of Navi so they can trek down to AutoBacs and install an unlocked 3rd party NAVI system. It's also cheaper that way too.