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

Project Prius needing Body Control Module

Discussion in 'Gen 2 Prius Main Forum' started by joe a., Jan 7, 2021.

  1. joe a.

    joe a. Junior Member

    Joined:
    Nov 22, 2014
    15
    3
    0
    Location:
    Salisbury, MD
    Vehicle:
    2004 Prius
    Model:
    II
    Could use some advice with my 2005 project Prius. I resurrected this vehicle from a friend who had it sitting in his driveway for the last three years. Body is excellent, but as you can imagine batteries were toast and all dash lights lit up like a Christmas tree.
    Believe it or not, this '05 has a plug-in receptacle on the rear bumper, plus a sun roof! When I went to replace the batteries there was an auxiliary battery in the spare tire well that I was able to verify its cost at $10,500! The sun roof added another $1,300. Almost killed myself removing the extra battery from the wheel well, as it weighed around 250 pounds. Got it all out and removed the wiring for the aux battery and sunroof. Lucky for me, there was no gas in the tank and she started right up after sitting overnight with a couple of gallons of high test.
    Here's where it got interesting. New batteries, tires, and happy to be running, finally got the abs and brake light out after bleeding the brakes, but still have one brake light, VSC light lit, and the red triangle along with the airbag light on.
    Hybrid battery now charges perfectly, good gas mileage, but triangle remains with the other two. A buddy with techstream tried to diagnose it for me but couldn't get into BCM, so I figure it needs replacement.
    I've tried but can't determine exactly where the BCM is located.
    Can anyone help me out here? I am real happy with the progress I have made. This Prius has only 120k miles on it, so it is worth it to me to continue on this project as long as the cost doesn't get out of hand. Any advice?
     
    #1 joe a., Jan 7, 2021
  2. ChapmanF

    ChapmanF Senior Member

    Joined:
    Mar 30, 2008
    23,791
    15,435
    0
    Location:
    Indiana, USA
    Vehicle:
    2010 Prius
    Model:
    IV
    You might find hobbit's write-up helpful.

    [​IMG]

    If Techstream isn't communicating with it, you probably want to check through the possible reasons why, before just blindly deciding the ECU must be replaced. For that, you would want to look in the repair manual (more info) at the troubleshooting steps for failure to connect to the body ECU.
     
    #2 ChapmanF, Jan 7, 2021
    SFO likes this.
  3. joe a.

    joe a. Junior Member

    Joined:
    Nov 22, 2014
    15
    3
    0
    Location:
    Salisbury, MD
    Vehicle:
    2004 Prius
    Model:
    II
    Many Thanks!! You have rescued me from an impasse and now I can finally look ahead.
     
    #3 joe a., Jan 7, 2021
  4. PriusCamper

    PriusCamper Senior Member

    Joined:
    Mar 3, 2012
    11,055
    4,499
    0
    Location:
    Pacific Northwest, USA
    Vehicle:
    2007 Prius
    Model:
    Two
    Well... There's an: ECM and more than one ECU, maybe even a PCM too? But I'm not aware of a BCM in a Prius? Maybe you got your acronyms mixed up? Perhaps you're looking for a "Battery Control Module" ? If so, we usually refer to that as the "Hybrid Battery ECU" and when it detects a problem the main ECU sets the red triangle and primary error code PA080 and then you have to ask the hybrid battery ECU for the subcode, which will point to the problem.

    So you can either get a buddy with techstream to try again, or you can buy an inexpensive OBD2 Bluetooth Adapter and install Dr. Prius app on your phone. Here's buyers guide: priusapp.com/obd.html And once you know the subcodes we can help you with the problem.

    The history of your vehicle dates back a decade when Prius enthusiasts wanted to turn it into more of an electric than just a hybrid car so they engineered a second battery pack that piggybacked on the primary pack and PriusChat was abuzz with those projects back in the day. It also led to several startup that thought they were gonna build a successful business selling these kind of packs, which you pulled out.

    But as you note they were very expensive and Toyota was like wow, this is a great idea and refined it and used near the same design to introduce the plug-in Prius in 2012, which wrecked the business plans of the startups and they all quickly went out of business.
     
    #4 PriusCamper, Jan 7, 2021
  5. ChapmanF

    ChapmanF Senior Member

    Joined:
    Mar 30, 2008
    23,791
    15,435
    0
    Location:
    Indiana, USA
    Vehicle:
    2010 Prius
    Model:
    IV
    Toyota's manuals call it the Body ECU, but if somebody wants to call it Body Control Module, that's not a huge obstacle to understanding what part they mean.
     
    #5 ChapmanF, Jan 7, 2021
  6. drone13

    drone13 Active Member

    Joined:
    Dec 5, 2020
    140
    115
    0
    Location:
    SoCal
    Vehicle:
    2008 Prius
    Model:
    Two
    You might want to take a look at the clockspring (spiral wound cable), in the steering wheel. Broken lines there can cause alerts on your dash for VSC, and Airbag since the clockspring is part of those systems with electrical lines for both. Many times that can show as steering wheel buttons, some or all, and horn not working also. You should be able to test that with Techstream. I have had to replace that on several Toyota vehicles in the past that showed the same dash warnings but no OBD 2 trouble codes.
     
    #6 drone13, Jan 7, 2021
    SFO and PriusCamper like this.
  7. ChapmanF

    ChapmanF Senior Member

    Joined:
    Mar 30, 2008
    23,791
    15,435
    0
    Location:
    Indiana, USA
    Vehicle:
    2010 Prius
    Model:
    IV
    By the way, you said Techstream wasn't able to communicate with the Body ECU, but what did it have to say about the brake/skid ECU?
     
    #7 ChapmanF, Jan 7, 2021
  8. joe a.

    joe a. Junior Member

    Joined:
    Nov 22, 2014
    15
    3
    0
    Location:
    Salisbury, MD
    Vehicle:
    2004 Prius
    Model:
    II
    I don't have an answer for that. I do know that before bleeding the brakes, the hybrid system was charging minimally and the BRAKE and ABS light were on. Now those two are off, and the hybrid system is now working properly and producing whole icons on the vertical 5-minute increments on the MFD. Vast improvement; brakes are normal and functioning properly. VSC light is on, and I have already replaced the clock spring with another one from a functioning prius. I realize I'll have to get hooked up w/techstream again, but thought I would put some miles on it and keep a close eye.
     
    #8 joe a., Jan 8, 2021
(You must log in or sign up to post here.)