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2006 w/ HID - headlights on = reverse camera & back-up lights

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by dcnelsonje, Oct 4, 2010.

  1. dcnelsonje

    dcnelsonje Junior Member

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    I have a weird problem with my 2006 with HID headlights and 78k miles. When I turn on the headlights, the reverse camera turns on & so do the back-up white lights. I can clear the reverse camera by pushing any button, but the back-up lights are a big problem.

    Anyone else ever experianced this, and what could the problem possibly be? No codes are being seen via ODB, everything else works great, and no fuses appear to be blown.

    Help !!!
     
    #1 dcnelsonje, Oct 4, 2010
  2. qbee42

    qbee42 My other car is a boat

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    It's either a bad ECU or a short circuit. I would expect a bad ECU to throw an error code, so lacking that, I suspect something has shorted your headlight circuit to a backup indicator. Where is the big question. I would first check for foreign objects in the fuse boxes.

    Tom
     
    #2 qbee42, Oct 4, 2010
  3. dcnelsonje

    dcnelsonje Junior Member

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    Could the problem be in the headlight assem itself? It was replaced about a month ago....

     
    #3 dcnelsonje, Oct 4, 2010
  4. firepa63

    firepa63 Former Prius Owner

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    Is that when the problem first showed up?
     
    #4 firepa63, Oct 4, 2010
  5. krg03

    krg03 Not expert, just experienced

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    Anything replaced at the dash area. Headlight switch, etc.?
    Headlight assem, you mean the headlights light?
    Guessing someone had the dash apart and something is shorting since you can clear the backup cam.
    The reverse lights and fuse/wires are under the dash. Connectors are at the drivers door panel. Headlight switch wires in the same place at the drivers door kick connectors.
    What happens if you just turn on the headlights before powerup? Backup lights on?
     
    #5 krg03, Oct 4, 2010
  6. dcnelsonje

    dcnelsonje Junior Member

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    I wish :) But no - we replaced the broken headlight w/ new and it was fine for about 4 weeks. Problem just started last night.

    My question is, where (and what) are the backup indicators, and could this be as simple as one of the running or tail lights shorting out on a reverse wire and causing the whole system to think (backwards, no pun intended) that it's supposed to be in reverse mode?

    Also, which ECU would be the one to check? I assume a very expensive & fancy piece of equipment would be needed too...

    Thanks again for all the help - I am freaking out right now.
     
    #6 dcnelsonje, Oct 4, 2010
  7. dcnelsonje

    dcnelsonje Junior Member

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    (Thanks for helping me think this through!)

    Nothing has been replaced in the dash area at all, ever to my knowedge but I am the second owner as I purchased the car about 3 months ago.

    Correct, headlight - the passenger side front headlight to be specific.

    I've always been able to clear the backup cam (prior to this starting) by pressing any of the display buttons - it turns off the camera, so it might not be a good clue as to what the problem is.

    I've looked over that fuse panel & can't find anything special.

    Are their connectors seperate from the fuse box under the drivers dash?

    So there could possibly be a short between the Headlight wires that lead into the fuse box and some other indicator that runs through the same fuse box that tells the back-up camera & lights to turn on? Do I understand that correctly?

    Also, I know this is a stupid question, but is there any way a blown fuse could cause something like this?

    If I turn them on before power up, nothing happens. But as soon as I power up - boom, back-up camera & back-up lights.


    Thank you again (to everyone) for the help - I can't find a good diagram that explains the back-up signals and lights so I'm lost at the moment.
     
    #7 dcnelsonje, Oct 4, 2010
  8. krg03

    krg03 Not expert, just experienced

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    ECU expensive.
    Electronic Control Unit controls just about everything.

    Probably has nothing to do with the headlight replacement (guess).
     
    #8 krg03, Oct 4, 2010
  9. krg03

    krg03 Not expert, just experienced

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    that is normal

    yes. just to the left of the park brake is a kick panel. connectors wires for reverse, headlights are there[/quote]

    Its a guess but yes they are located in that area. Backup cam I can't remember if it's at the driver side... Power is being applied when the headlights are on that tells the car its in reverse.
    [/quote]
    no. BUT did you blow a fuse anytime? Could indicate the short

    Before powerup I turn the light switch off and then on. The headlights come on. Yours? Are the backup lights on also?
     
    #9 krg03, Oct 4, 2010
  10. RobH

    RobH Senior Member

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    I'm thinking that it could be a bad ground connection on the taillight module. Are the lights all at normal brightness?

    Say there's a bad ground on a taillight. You turn on the headlights, along with the amber markers. The amber fronts are probably on the same circuit as the red taillights. The power gets to the red taillight, but can't get to ground since there is a bad connection. But the floating ground does go to the backup lights. So you've reverse fed 12V to the backup light. Circuit continues on to the other backup light, which has a good ground. End result is the backup lights are on (but dim), and the "in reverse" signal is active (= backup camera).

    Check if the 4-way emergency blinkers show the same brightness on the rear. A dim one is probably the one with a bad ground.
     
    #10 RobH, Oct 4, 2010
  11. krg03

    krg03 Not expert, just experienced

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    Thats a good guess! Ground seeking through another circuit. Could be from something other than the headlights - as you said maybe the tail lights.
     
    #11 krg03, Oct 4, 2010
  12. dcnelsonje

    dcnelsonje Junior Member

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    Thank you so much - I'll be checking it all out again this afternoon when I get home. Fingers crossed :)
     
    #12 dcnelsonje, Oct 5, 2010
  13. priusbee

    priusbee Member

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    The backup light is activated by a relay. Check the relay. Try removing the relay. There should be no power to turn on the backup light if the relay is removed. If you see a similar relay, try swapping to see if the problem goes away.

    Contact inside the relay some time goes bad and it is sticking, you can open up the relay and clean it with a 400 sandpaper. Or, just buy a new relay.
     
    #13 priusbee, Jan 2, 2013
  14. cwerdna

    cwerdna Senior Member

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    ^^^
    Did you notice that you resurrected a thread from over 2 years ago?
     
    #14 cwerdna, Jan 2, 2013
  15. priusbee

    priusbee Member

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    Just in case someone has a same issue and maybe it will help the them. That is what a forum is for, to help people who wants help.
     
    #15 priusbee, Jan 2, 2013
  16. mikepri

    mikepri New Member

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    Got the same issue. Same year and HID. Did you ever get it fixed? Just trying to find out what the final answer was.
     
    #16 mikepri, Dec 4, 2013
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