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

2018 Prius Brake Booster Master Cylinder

Discussion in 'Gen 4 Prius Technical Discussion' started by safetywest, Feb 13, 2023.

  1. safetywest

    safetywest Junior Member

    Joined:
    Aug 17, 2021
    8
    4
    0
    Location:
    Arkansas
    Vehicle:
    2018 Prius
    Model:
    One
    Hello,

    I own a 2018 Toyota Prius with around 70k miles and I am the first owner of the vehicle. A couple of weeks ago, I was parking the car on a hill and all of a sudden I lost steering, a bunch of lights popped on the dash, horn, windshield wipers, radio, heater, windows, etc. failed. I was able to drive the car on a tow truck and tow it to the dealership.

    The dealership informed me that, the 120 amp fusible link block assembly needs to replace. After replacing that, they find out the 30 amp ABS fuse was blown as well. The last phone call I received from the dealership a couple of days ago stated that they now come to find out if the brake booster master cylinder or brake actuator needs to replace(One of the other, I couldn't remember since he was explaining over the phone).

    However, they're not %100 sure replacing that part will fix the problem. The person over the phone said, the brake booster actuator has short and he believes that's what causing the issue. When they disconnect the part, seems like the problem goes away. This is a very costly repair and the car is fairly new(Around $2200-2500 including part and labor) I've been told it's not covered under warranty. I'm just trying to figure out if Toyota covers this issue since it wasn't a user issue? Or has anyone had an experience like this before?

    Even the dealership said this is a pretty big repair, they don't see this often on Toyota.

    Thank you!
     
    bisco likes this.
  2. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    107,574
    48,862
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    probably not, at 70k, but call toyota customer service, and ask for goodwill warranty help.
    that is a very early failure, and has to be defective.
    i would also ask for a guaranty that it will solve the problem. sounds like the dealership is not sure
     
  3. safetywest

    safetywest Junior Member

    Joined:
    Aug 17, 2021
    8
    4
    0
    Location:
    Arkansas
    Vehicle:
    2018 Prius
    Model:
    One

    I will call tomorrow and ask for a goodwill warranty, never heard of that before. What do you mean to ask for a guarantee? I'm confused
     
    bisco likes this.
  4. Elektroingenieur

    Elektroingenieur Senior Member

    Joined:
    Jan 8, 2017
    2,515
    3,253
    9
    Location:
    California
    Vehicle:
    2016 Prius
    Model:
    Three Touring
    A blown 120 ampere DC/DC link in the fusible link block assembly (seen in my previous posting) and a blown 30 ampere ABS-MAIN or ABS MTR NO.2 fuse would be consistent with a short circuit in the brake system. The Electrical Wiring Diagram (more info) shows that those two ABS fuses don’t serve any other loads, though a fault in the wiring, connector, or junction block could have similar effects.
    There’s no part called the “brake booster actuator”; rather, the three major assemblies in the electronically controlled brake system are:
    You can read all about each assembly and what it does in New Car Features (more info). Each assembly is sold only as a complete unit; the Repair Manual doesn’t describe any internal repairs or adjustments.

    The problem is to be sure which of these parts (if any) has a fault, and to be sure that the trouble isn’t actually in a wire or connector. If it were my car, before I’d authorize any of the expensive assemblies to be replaced, especially if the dealer isn’t completely sure of the diagnosis, I’d ask them to explain their troubleshooting process in detail, and I’d check their work against the Repair Manual (more info) procedures. Did the dealer scan for diagnostic trouble codes, and which ones did they find? Exactly where did they make electrical measurements, under what conditions, and what were the readings?
    As described in the Warranty & Maintenance Guide (PDF), since the basic warranty has expired, and the brake system isn’t covered under the hybrid system, emission control, or other warranties, Toyota wouldn’t have an obligation to pay for the repairs.

    That said, as @bisco kindly suggested, you could ask Toyota for goodwill consideration. “Goodwill,” in the industry jargon, is when an automaker offers to pay some or all of the cost of a repair that wouldn’t otherwise be covered under any warranty, in the interest of good relations with its customers. It’s a fair request here: the major assemblies of the brake system should last for much longer than 70,000 miles, and a premature failure, unless there was some outside influence, suggests a latent defect.
    I think @bisco's idea is that the dealer should share the risk of their diagnosis being wrong. If putting in one expensive part doesn’t fix the problem, or worse yet, also causes the new part to be damaged, you’d want the dealer to pay any further costs to complete the repairs. I’m not sure this is something a dealer would agree to, however.
     
  5. safetywest

    safetywest Junior Member

    Joined:
    Aug 17, 2021
    8
    4
    0
    Location:
    Arkansas
    Vehicle:
    2018 Prius
    Model:
    One

    Thank you, your comments give me a little bit better understanding of the whole issue. They're going to replace The brake booster with master cylinder assembly. I spoke with the service manager and he said when they diagnose, they have to follow the chart and steps that Toyota suggests. He also states, when they remove the part, the short goes away. So I hope they already test the wires and such before replacing the part. At this point, they're so hard to work with and they're getting frustrated over the phone for no reason.
     
    bisco likes this.
  6. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    107,574
    48,862
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    I just mean, what if they replace it, and the problem doesn’t go away
     
  7. FuelMiser

    FuelMiser Senior Member

    Joined:
    Jun 29, 2008
    1,263
    858
    0
    Location:
    Monument, CO
    Vehicle:
    2016 Prius
    Model:
    Touring
    My first thought was rodent damage. Is the car parked outside? Or could it be water/flooding damage?
     
    safetywest likes this.
  8. safetywest

    safetywest Junior Member

    Joined:
    Aug 17, 2021
    8
    4
    0
    Location:
    Arkansas
    Vehicle:
    2018 Prius
    Model:
    One

    I agree with you on that %100. I was trying to say that to the dealership but I was told, they won't know the next step or can't further diagnose until the faulty part is fixed. At this point, they're saying that The brake booster with master cylinder assembly needs to replace and then check again to see if it's fixed. I think it's bs but they said that's how service centers work.
     
    bisco likes this.
  9. safetywest

    safetywest Junior Member

    Joined:
    Aug 17, 2021
    8
    4
    0
    Location:
    Arkansas
    Vehicle:
    2018 Prius
    Model:
    One
    I spoke with Toyota for a goodwill warranty, but they said I'm not eligible.