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Cracking a Toyota's code

This Prius brake-by-wire system may be new technology, but old-fashioned troubleshooting led to the fix.
Wednesday, June 27, 2012 - 06:29
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The part came two days later, and I plugged it in. Next I took my Toyota/Mastertech scan tool and perform the required initialization of the linear solenoid and calibration of the steering angle sensor and I was ready for the moment of truth! A 1 volt drop on that circuit with the phantom F16 fuse or not, here we go. Brake apply, power button pressed, car fixed! No telltales, no DTCs and no pulsing pedal. I hate to say this but once in a while the sensible thing to do is to stop “splitting atoms” and just try a part that makes sense.

The Last Word
Finally it was time for a road test, which went without a hitch, and then back to the shop to drop that Toyota smart key fob for that overly smart brake-by-wire Prius back in my common sense smart wife’s hand. After a big hug she admitted, “Honey, I’m sorry about the ‘tow the car to the dealer’ comment. I never lost faith in your mechanic skills – I was just trying to light a fire under you to get my Prius back!”

For the technical last word, now that I understand the system, it makes sense the Skid Control Module could cause all the symptoms experienced. But what about the 1 volt drop on the power feed to the Brake Actuator Module? Was it the cause of the Skid Control Module’s demise or a normal condition in my measurements that could possibly be explained by some information missing from the service manual? Will this good used Skid Control Module fail someday, too? Good questions to ponder but for now I’m focused on celebrating two accomplishments: the return of marital bliss and cracking the code of Toyota’s hybrid brake-by-wire system.

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