1. Attachments are working again! Check out this thread for more details and to report any other bugs.

2011 C1391 Troubleshooting Verification

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by kgbnick, Nov 22, 2019.

  1. kgbnick

    kgbnick New Member

    Joined:
    Nov 22, 2019
    2
    0
    0
    Location:
    Orlando, Florida
    Vehicle:
    2011 Prius
    Model:
    III
    I have a 2011 III and recently had my ABS, Brake System, and Slip Indicator warning lights come on.

    I threw Windows on my MacBook, got Techstream and a cable, and a subscription to AllData. I discovered I had a C1391 DTC code.

    Going through the AllData troubleshooting guide, I got to the point where I am to clear and reconfirm the DTC code. When I clear the code and re-scan, no DTC C1391 is output. According to the AllData troubleshooting guide, this means I'm to "REPLACE BRAKE BOOSTER WITH MASTER CYLINDER".

    Questions:
    1. Is there additional testing anyone would recommend to make sure this is the actual/only issue I'm dealing with?
    2. The AllData C1391 troubleshooting guide links to a removal guide under "Vehicle » Brakes and Traction Control » Power Brake Assist » Vacuum Brake Booster » Service and Repair » Removal". I assume this means I need to replace the "Vacuum Brake Booster", which takes me to two different parts based on tires, but the part numbers (4705047140) are identical. Is the "Vacuum Brake Booster" the same as the "Brake Booster with Master Cylinder Assembly"? Assuming it is, am I correct in understanding this is the piece that does have an ECU so my easiest bet would be to make sure I get a 2011 instead of trying a 2012 that may need reprogramming?
    [​IMG] ​

    Thanks!
     
    #1 kgbnick, Nov 22, 2019
  2. ChapmanF

    ChapmanF Senior Member

    Joined:
    Mar 30, 2008
    24,005
    15,605
    0
    Location:
    Indiana, USA
    Vehicle:
    2010 Prius
    Model:
    IV
    If you're talking about a Prius, there is no such thing anywhere as a "vacuum brake booster." The Prius engine isn't always running to produce vacuum, and there is nothing, nothing in the car that is vacuum powered.

    Before spending the time and money to replace either part (the master cylinder/booster, or the accumulator/booster pump), I would be tempted to look for the same troubleshooting procedure in the Toyota repair manual (more info), just to make sure it doesn't maybe have a more informative troubleshooting procedure than what you got from AllData. Ideally, by the time you are done studying the manual and following the procedure, there should be a good idea in your head of which assembly you suspect and why.

    And at least the Toyota manuals won't be talking about mythical vacuum boosters. :)
     
    #2 ChapmanF, Nov 22, 2019
    Robert Holt likes this.
  3. kgbnick

    kgbnick New Member

    Joined:
    Nov 22, 2019
    2
    0
    0
    Location:
    Orlando, Florida
    Vehicle:
    2011 Prius
    Model:
    III
    Based on TIS, looks like T-SB-0024-19 suggests I might be able to get this fixed under warranty. The official troubleshooting directions are identical to AllData/Chilton. The troubleshooting steps point me towards replacing the "Brake Booster AssyW/MasterCylinder" (original part number 47050-47140 OR 47050-47150 replaced with 04008-11147 OR 04008-11247). However, T-SB-0024-19 says to replace that AND "PumpAssy, Brake Booster" (original part number 47070-47060 replaced with 04006-22147). So I'm definitely starting with the dealership to see if they'll take care of it, although I'm not sure what to do since I cleared the C1391 code. If they won't do it, I'll have to see if I can afford both parts or just start with "Brake Booster AssyW/MasterCylinder".
     
    #3 kgbnick, Nov 22, 2019
(You must log in or sign up to post here.)