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Dome power loss with VSC light on

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Zembu, Jul 15, 2015.

  1. Zembu

    Zembu Junior Member

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    Silver Spring, MD
    Vehicle:
    2007 Prius
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    N/A
    4 weeks ago just after starting my 2007 prius the VSC light came on and along with it, I didn't have power to my audio system, interior lights, clock, or keyless entry/start. A few days later after checking to make sure the dome fuse wasn't blown, the light went away and power was restored. A few days after that, I had to use the manual key to gain entry to the car and after inserting the fob into the slot and starting the VSC light was on with all the previously described power loss. This was the definition of an intermittent problem and it continued that way for about 2 weeks.

    During that time, I took it to an independent shop I trust and they pulled the code, C1231, that was associated with the VSC light. They told me I needed to take it to a dealer.

    While dragging my feet for another 2 weeks, the VSC light is now on all the time with the corresponding power loss. Aside from no power to these systems the car drives fine. I did check the 12V battery and it is fine.

    So this week I finally found a dealer who would look into it without charging me a diagnostic fee. I just got the car back today without anything being fixed and me not agreeing to their suggested fix due to cost. The following is the work text and their recommendation:

    "Code C1231 Steering angle sensor
    Unable to delete DTC & Steering angle does not change
    Checked Fuse 10A Dome: tested okay
    Checked for power at Junction connector J6: Power Present
    Junction 23 has no power
    When back to to instrument panel relay location & checked pin #13 at connector 1A: No power
    Open circuit between 1A & J6 Junction Connector
    Recommend replace instrument panel wire harness $5,100"

    Does anyone have any suggestions as to other things to try besides replacing the instrument panel wire harness? Or does anyone know of a non-dealer shop in the Washington, DC metro area that specializes in Prius troubleshooting?

    I'm certainly not going to drop that amount of money on a repair as that is basically the current value of the car but I do miss the convenience of the keyless entry and start, the clock, and playing music while driving.

    Thanks in advance for any suggestions and help.
     
    #1 Zembu, Jul 15, 2015
  2. valde3

    valde3 Senior Member

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    It’s easy to verify their findings. Just test that there’s no continuity between junction connector J 6 and pin 13 of connector 1A. If there isn’t you do need to replace or repair the wiring harness. Maybe you could get used one? This isn’t a common failure so used one should be ok.

    I wouldn’t use the car like that because you don’t know what the problem is. It can cause (almost) anything at any time.
     
    #2 valde3, Jul 16, 2015
  3. Patrick Wong

    Patrick Wong DIY Enthusiast

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    I'm really surprised that dealer did not charge you for the time spent by the tech, which easily could have been one hour, to discover the findings which were documented. It sounds like that tech knows what he is doing with regards to troubleshooting electrical issues.

    1. Was the car in a front-end accident or flooded at some point in its history?
    2. If the car was not in an accident, was it infested with rodents? Check the cabin air filter for example.
    3. Inspect the wiring harness for obvious damage. J6 is located on the passenger side of the car near the engine and HV ECUs behind the glove compartment, and of course the relay box is under the instrument panel, driver's side.
    4. Remove the affected wiring harness connectors and spray with electrical contact cleaner. Maybe that will help.
    5. Run a replacement wire from J6 to pin 13, connector 1A at the relay box. That might work if only one connection is having a problem.
    6. See if the independent shop is willing to install a used electrical wiring harness, which is labor intensive as the dashboard must be totally disassembled for access. That might cost $1K or more in labor effort, not to mention the cost of the used part.

    If you wish to DIY, subscribe to techinfo.toyota.com to obtain electrical wiring diagram information which is required to understand the problem and figure out where the relevant junction connectors and wiring harness connectors are located.
     
    #3 Patrick Wong, Jul 16, 2015
    Last edited: Jul 16, 2015
  4. andrewclaus

    andrewclaus Active Member

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    If it were me and I had a few hours free time, I'd try to find the discontinuity and repair it. I've been looking at the wiring diagrams in my Bentley manual and there's enough information in there to back up the diagnosis. If it were my car, I'd probe a bit under the dash, at least try to see if there's mechanical damage to the connectors or cables, or some corrosion somewhere. If you're really good with wiring diagrams and a soldering iron, or really lucky and/or creative, you may get it. Good luck.
     
    #4 andrewclaus, Jul 16, 2015
  5. Zembu

    Zembu Junior Member

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    2007 Prius
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    N/A
    About not being charged, I called and specifically asked what their diagnostic fee would be to investigate the reason for VSC light. I think I was dealing with a secretary who went and asked and I suspect she asked about a check engine light which a lot of shops do investigate for free. After she told me it would be free, I confirmed that it was for a VSC light and told her that was the only reason I was making the appointment and asked her to make sure it was noted. Of course when I dropped the car off, the service rep wanted me to acknowledge a $142 diagnostic fee. I told him the same thing I wrote above and he reluctantly let it go as a free diagnostic. He did tell me that after they spent an hour on it, he would have to call me back to have me authorize them spending more time by agreeing to a diagnostic charge. I know they spent more than an hour but he never called me for further authorization. Ultimately, I think he felt bad that the suggested repair was so much and just decided not to charge me.

    1. No accidents or floods with this car.
    2. Interesting that you suggest this. When I was checking the dome fuse, I removed what looked like the partial remains of a mouse from the upper right area under the hood closest to the windshield. I think your suggestion of a rodent problem may be the cause for my trouble. Since you suggested this, I assume you've seen it in other cases. How did the damage from a rodent show up? Is it in a wire or wires being chewed?

    Thank you for the suggested steps to try and resolve it. I'll see what I can do over the next couple of weeks and post again when I have something of consequence to share.
     
    #5 Zembu, Jul 16, 2015
  6. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Yes. I think you have a reasonable chance to resolve this yourself if you remove the plastic dashboard cover so that you can fully examine the wiring harnesses in the dashboard area. This is not a trivial task though, you need to deal with the passenger-side airbag which requires special handling, disconnecting the 12V battery first, etc. Expect to see a wire or wires with damage from chewing. Once you have identified the damaged wires then you can splice or solder around the damaged wires. Soldering is best if you have that skill.
     
    #6 Patrick Wong, Jul 16, 2015
  7. Zembu

    Zembu Junior Member

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    2007 Prius
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    N/A
    Unfortunately I don't have the skills to fix this myself. I could probably get the dash off with the help of a youtube video and some effort but I wouldn't know how to fix damaged wires myself.

    I took my car to a DC area electric specialist and they quoted me $1,200 to take the dash off and fix any bad wires. Seems steep to me so I'll be exploring other options where family lives in PA at a shop that has a much lower hourly labor rate.

    It will likely be another month before I can get that done so I'll just continue to drive my otherwise functioning car for another month.
     
    #7 Zembu, Aug 18, 2015
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