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

daytime fog lamps

Discussion in 'Gen 2 Prius Accessories & Modifications' started by psibill, Feb 22, 2007.

  1. psibill

    psibill Junior Member

    Joined:
    Jun 29, 2006
    55
    1
    0
    I'm pretty sure I saw this here--a way to "reprogram" so that the fog lamps would be on at the same time as the headlights.

    Now, I can't find that thread. Reason for looking is that my fog lamps are never on. Not when the headlights are on, nor with just the running lights. So I'm thinking maybe something got "reset" in the programming department.

    Thanks.

    --Bill
     
  2. Bill Merchant

    Bill Merchant absit invidia

    Joined:
    May 3, 2005
    4,096
    82
    13
    Location:
    USA | Oregon | Portland area | 97004 |
    Vehicle:
    2007 Prius
    I think a fuse maybe got reprogrammed to open. About the only way your fog lamps will work is if your headlights are on (barring some cutting and dioding under the dash). If your fogs aren't on, I bet a fuse is blown.
     
  3. Charles Suitt

    Charles Suitt Senior Member

    Joined:
    Oct 8, 2004
    1,637
    16
    0
    Location:
    Dallas TX
    Vehicle:
    2012 Prius
    Model:
    Four
    <_< I don't recall who originally posted this, but I saved the file on how to enable fog lights anytime. Here's the text: APOLOGIES TO THE ORIGINAL POSTER...

    Rewiring fog lights on my 06 pkg 6. Since I Have HID's, standard 1/2 voltage DRL's arent' possible. It took a bit of work and it isnt for the faint of heart but works like a charm. Now to upgrade the bulbs themselves.

    First, the Fog Light relay under the hood (long relay box in center of engine compartment) only has power when the park lights are on. Starting here, unbolt the 2 10mm bolts and flip the box over, remove the cover and you will see the back of the relays. Locate the Fog lamp relay (2nd from left) and cut the BROWN wire a few inches away. You will now connect this to the PURPLE of the PTC HTR 2 relay next to the fog relay. This is an IGNITION - ON feed and allows the relay to be triggered only when the Igntion is ON. Put everything back together. Now the relay can only operate when the car is ON - instead of only when the lights are on.

    Next pop the bottom cover off of the steering column and access the flasher/lights plug( See knowledge base info under EV switch for details) Find the ORANGE wire (fog light switch ground - provided by low beam switch)...cut it and jump the switch side to the DARK GREEN wire in the same harness(low beam switch ground). Tape off the other cut ORANGE wire end and your done here. Put the column back together. You have now allowed the FOG switch to use a CONSTANT ground signal, unaffected by the headlight switch.

    This is the hard part, following other instructions on the site, You can either follow the directions for accessing the 2 wires given in the Knowledge BAse article about making the Fog Lights work independant of low beams or do it my way(easier on the back . Drop the lower dash panel, remove the 3 10mm nuts securing the metal plate, and then the 3 10mm bolts securing the fuse box/body ECM to the dash (top 2 bolts are machine thread, left bolt is a coarse thread into plastic). Release and unplug all of the plugs on the FRONT (side facing the driver's seat) of the fuse box. MAKE SURE THE CAR IS OFF before doing this. (this will erase the clock and MPG memory).

    At this point, it will be easy to rotate the fuse box around and see the Body ECU plugs on the back top. 3 plugs. You want to unplug the one closest to the drivers side.

    Locate the YELLOW and Lt. BLUE wires in pins 13 & 17 (they are caddy -corner to each other). Cut them off and connect the car sides of the wires to each other. Tape off the ECU sides and put everything back together. You have now just bypassed the Body ECU's ability to regulate Fog light usage.

    So, now, when you turn the Fog light switch ON, you provide a direct ground to the Fog Light Relay under the hood which receives it power now from Ignition. The Fog lights can now be left on and will come on when the vehicle is started. They are totally unaffected by head/park light usege.


    I have not made this modification... not sure I will. I can't attest to its validity.
     
  4. subarutoo

    subarutoo New Member

    Joined:
    Jan 18, 2006
    1,213
    23
    0
    Location:
    Chatsworth, CA
    Vehicle:
    2006 Prius
    In most states, its illegal to drive with only fog lights on. Also illegal to drive with fogs and high beams at the same time. People do, but check the vehicle code.