Fog Lights: Install [Retrofit] fog lights on 2010 Prius?

I'm located in Louisiana and my dealer told me the same thing.

 

Absolutely right, hawkmoon. The fog relay gets its 12V coil voltage switched from the tail light relay and fuse. See the attached page from the instrument Panel Junction Block inner circuit drawing. The fog relay is inside this junction block, in the instrument panel, next to the Main Body ECU.

And I just noticed something else on this attachment. BOTH pins 7 and 8 on 2C could be used for the 12V wires to the fog lights. I have no idea how much current each of those pins can carry. Ordinarily, that would mean that hose two pins are intended to only carry a max of 7.5A each. (fused at 15A) However, the rest of the fog light wiring diagram on TIS shows that only pin 8 is used, and it's split somewhere near the headlight connector CA1, at the front bumper.

CASUMIK, if your service tech is pulling 12V inside the engine compartment, it's not from the fog relay. I'll be interested to see what exactly the tech connected to by drilling into the body fuse box.

 

Rachaelseven, thanks much for posting this. My dealer was having a hard time finding this pin.

I had decided not to download those connector pin drawings from the TIS site - now I wish I had....and the parts tech at the dealer didn't know how to get to those drawings on TIS, and I couldn't remember, either. Can you remind me how to get to those pin details on TIS?

He said the part number for the pin is not even in his system, and he has to order them from Japan. He said, "see you in 2012..." What a comedian...

 

You are very welcome. To find the connector P/N stuff on TIS, you select the system you want and go either to the connector list or the wiring diagram. You then select the connector and click the little 'harness repair info' button, which brings up the pin information.

 

I have looked all through the EWD's and I found absolutely no reference to a shift lever LED, light or lamp. There is one that is shown in the "Map Light Assembly" that might be it, on the tail light circuit drawing (which would make sense, because it comes on with the tail light). It is a green wire, and comes from pin 35 on connector 2A on the instrument panel junction block (next to the Main Body ECU), through pins 1 and 3 of Junction connector L88 and through pin 16 of UL1, both on the left side of the dash, then up the support to the roof, to either pin 7 of U13 (with sunroof) or pin 8 of U3 (without sunroof), at the map light assembly. The white with black stripe going to pin 1 of U3 or pin 9 of U13 is the ground wire for the LED.

Again, I'm not sure this is it - but the EWD symbol indicates that this is an LED, not a lamp - and I think that's the only LED in the Map Light assembly....

Hope this helps.

 

That was what I forgot. Thank you!

 

He is getting the current from the fog relay under the dash, I can hear it click when I turn the stalk, I will upload the drawings they gave n
me showing the fusebox / ecu under the dash. he says the pins are not listed in his parts list.the pins for the connectors that are at the fog lights themselves. As far as the relay under the dash I'll have to check my parts list to see what pin #s he used to connect there.will try to post tonight when I get home.

 

Maybe I should say junction box, is that the same as fuse box? I M a landscaper not an electrician! He connected under the dash

 

In this case, "junction box" would be correct, as I do not think there are any fuses in this particular box under the dash. So your technician must have run a wire through the firewall, as we'll have to do too... I wonder how he did it?

 

Actually, yes, there are fuses in that junction box assembly - see Owners manual page 468. They are accessed from underneath the dash.

Perhaps CASUMIK's tech used the fog relay output, but used it to "feed" a second circuit through some installed but "unused" wiring (don't know what that would be...) I have thought about doing this myself, but haven't looked into it yet.

 

No worries. I'm a lawyer, not a mechanic! We may all be new to this, but it is not stopping some pretty handy mods.

 

he definitely used the fog relay output and i thought ran the wire straight from the fuse box to the lights.i ll have to call him monday. Below are the diagrams they emailed me( i have 4 more but they seemed unrelated or redundant,let me know if what i attached is helpful or not the first one is the stalk,the second i believe the relay position in the main body ecu(fuse box). I looked at the fuse box cover and the fog light fuse position is labeled there and there is 1 15 amp fuse in the slot(i assume he put this in )thanks again for the encouragement hawkmoon!, i am much more comfortable in the garden

 

Hey guys,

Can you tell my why/if this would be a bad idea:

Wire the foglights so that they come on automatically with the headlights. You could tap into the headlight +12v line under the hood, run that to a relay that turns on the fog lights. That way all the wiring is under the hood, you never have to cross the firewall, and you don't have to have any kind of switch in the cockpit. Also since the car automatically turns off the headlights when you turn on your brights, your foglights would go off too.

Would this work at all? Do the headlight bulbs use straight +12v?

 

It seems to me that you'd be using a lot of electricity unnecessarily, as this scenario would mean that your fog lights are on all the time your headlights (low beams) are on, whether you need the extra light or not. Fog lights drink quite a bit of juice, which will negatively impact your gas mileage...

 

I did the fog light install but not with the turn signal stalk. I bought the lights and housings at Toyota so they would look stock and would be legal in Virginia. What a lot of people do is go with the after market fog lights and then not realize a observant inspector can fail you. There has to be a DOT reference on the lens. I mounted a lighted switch in one of the blanks and wired it through the outside fuse box. It's not factory, but it is functional. The dealer gave me a $1500 quote for everything and I did it for under $500 including labor.

 

It should work fine. It will add about an extra 90 watts to the system.

 

Do you have pics of what you did. I'm more of a visual based person. However your way seems like the way I want to go. Not all factory but close enough to feel good about the way it looks. Thank you all for all your help as well as experimentaion.

 

I already ordered the headlight stalk, so too late for me. I already regret it though because it is going to be a very difficult installation. Everythign is the same as installing the kit, except that instead of plugging the wires into the switch that comes with it, I will have to remove the stearing wheel, and it also looks like I will have to remove the entire main body ECU to get access to the internal relay. I did this once before and it was NOT easy. And even after doing all of that, I'm not sure just how to tap into the relay.

I'm thinking it will be alot easier to just use the relay in the provided kit, leave everything under the hood, and then run one wire from the relay to the interior cabin. That wire would just plug into wire in the headlight stalk. No ECU to remove and disassemble, and it would operate the same way as stock.

 

If we can buy the right terminal for the ECU connector (not available yet), we can tap into the relay simply by adding one pin to the connector. I agree that taking apart the steering wheel will be no fun and I might yet chicken out on that, but tapping the relay at the ECU should be pretty straightforward once we are able to order the parts (Terminal P/N 82998-24350 & Press Sleeve P/N 82999-12030).

 

What you describe should be fine, with two caveats:
1. Using the Headlight +12V is fine as long as it only controls a relay coil, as you describe. That line shouldn't be used to provide the actual 12V supply to the fog lights themselves. The fogs will require anywhere from about 6 to 8 amps under normal operation, and your headlight circuits probably aren't designed to handle that amount of excess current.

2. Whatever circuit you "tap into" to supply the 12V fog light power must be able to continuously handle that excess current.

I may sound a bit like a broken record on this - but I see this in my work too frequently (I'm an electrical engineer by trade). While the circuit may "work", and may never even blow a fuse, the wires can run hotter than intended due to the increased current, which over time breaks down the insulation, makes the insulation brittle and prone to cracks, which can then allow oxidation of the copper wire inside (oxidation = even hotter wires) and moisture intrusion, making everything worse. Over time, the insulation can crack off and expose wiring to shorts, etc., where it runs near or is attached to metal tie-down locations.

Always, always, always consider the additional current you are adding to an existing circuit, both in terms of fusing and the wiring itself. I have no idea how much "excess current capacity" Toyota builds into its wiring designs. Running a separate dedicated circuit is usually cheap. Replacing a factory harness - that can be expensive.