Automatic Headlights

Another satisfied customer ... this turned out straightforward to do (using the existing light sensor on the dash and the existing feature in the body ECU) on my 2010.

Like others going the same route, all I had to do was complete the run of one wire from the light sensor on the dash to the body ECU (L7 pin 21) ... and then one more wire to tell the ECU when I want auto lights (L7 pin 28 to ground when I want lights that switch on automatically).

Ultimately, I expect I'll run that second wire to L47 pin 19 on the steering column, and plug in a Canadian-style headlight stalk with the AUTO position, but I haven't yet.

I'm happy to report there's a great benefit of just running the light sensor wire, even if that's all you do. As long as there is a light sensor signal to the body ECU, it will use that signal to brighten and dim the dash lights (when the taillights are on), even if you still just turn your lights on and off manually. So you can keep the dash nice and dim for dark night driving, and still be able to read it around dawn or twilight, and not have to fuss with the dimmer knob. To me, that's a bigger deal than whether it actually turns the headlights on and off for me, so it's worth the price of admission even if you never add the other wire or do anything for an auto switch.

I was also happy to accidentally discover something I don't think is in my owner's manual. After getting out of the car, the lights stay on for a while: 30 seconds by default, though techstream can change it to 60, 90, or zero). The manual says all that, but doesn't mention that you can press the lock button on the fob an extra time to turn the lights off right away. At least, if it is in the manual I missed it, but it definitely works.

Being a 2010, my car was missing both segments of the wire from the light sensor to the body ECU: from I1 pin 4 at the sensor to LI1 pin 12 (male) behind the upper glove box, and the one that continues from there (female) to L7 pin 21 at the ECU.

Getting the hang of the interactive wiring diagrams at techinfo, all I had to do was point and click on each of those two lengths of wire (which made I1, LI1, and L7 all blink), then also click the wire between L7 and L47 pin 19 on the column (L47 starts flashing too), then click the Info icon, expand the Wire Harness Repair links, click the Print button, and generate the handy PDF attached, showing all the connectors with the right positions highlighted, with the terminal part numbers and dimensions. This is a great tool.

I'm also starting to get the hang of their terminal nomenclature. From the wiring diagram info, you can see there are general categories:

	Position	Type	M/F	P/N 82998-
1	I1:4	0.64 non-waterproof	F	12750
2	LI1:12	1.5 non-waterproof	M	24340
3	LI1:12	1.5 non-waterproof	F	24350
4	L7:21	0.50 non-waterproof	F	N/A
5	L7:28	0.50 non-waterproof	F	N/A
6	L47:19	0.64 II non-waterproof	F	24290

You start to see that the basic categories are non-waterproof and waterproof terminals, in families identified by pin size (0.64, 1.5, 0.50 mm, etc.) and that for some pin sizes there are also distinct families (0.64, 0.64 II, etc.) Using that information from the wiring diagram, it might be possible to find compatible terminals (my local independent auto electric shop suggested to try GM dealers; he says GM uses many of the same terminals, and they sell them bare, not precrimped and overpriced as Toyota does).

It's a drag having no part numbers for those tiny 0.50 mm female L7 terminals. The terminal looks like this:

End-on, it is about 1 mm square, tiny little thing.

The L7 housing is a bit unusual. It separates into three decks. Separating the decks is easy when done right. On the front of the connector, along each between-deck parting line, can be seen two notches for thin screwdriver blades. Twisting blades in those notches will gently pop the decks apart at the front. They then unhook at the rear. Reassembly starts by engaging the hooks at the rear, then snapping the decks together in front.

When the decks are snapped together, they are also the secondary retention mechanism for the terminals. There are bits of each deck that fit into slots in the adjacent deck, behind the terminals, and will keep a terminal from pushing back out even if the primary retention lance doesn't hold for some reason.

The primary lances are formed in the housing, not on the terminals.

Not being able to buy these female terminals, I made what seems to work pretty well, using some special thin wire made for wire-wrapped connections on circuit boards, and a wire-wrap tool, and a round metal form about 0.7 mm in diameter to wrap the wire around. (I have a bunch of old cut-off lead scraps from circuit board assembly, and found one really close to 0.7 mm diameter.)

I stripped the insulation off one end for about 24 mm, fed it into the wrapping tool, and wrapped it around the 0.7 mm form, where it made 8 or 9 wraps (I wrapped them spaced out like a spring, instead of as tightly together as possible). I slid the little coil off the form, stretching it to be about 7 mm long. It slides easily into an L7 housing cavity from the rear and is the right length so that, when it's inserted fully, the secondary retention nib (when the decks are snapped together) fits right behind it and holds it in place. The connector mates easily with the body ECU and the contact seems to be plenty good for the low-power signals it has to carry.

This wire-wrap wire is pretty thin, frail stuff, though, so I just used short lengths from the L7 connector to a screw terminal block I solidly mounted nearby, so there shouldn't be much stress on the angel-hair wire, and at the screw terminals I transition to ordinary wire. (You can see the pin 28 wire just going to a grounded screw for now, giving me perma-auto-lights until I add a switch.)

In fact, even to clamp it in the screw terminals, I started by using the wrap tool again to wrap those ends of the wires over some more scrap cut-off leads, wrapping the stripped portion and several turns of the insulated portion, with some heat-shrink tubing to stiffen it all, leaving just some bare scrap lead sticking out to clamp in the terminal block. I used different color heat-shrink to make sure I could remember which of the two wires (for pin 21 and pin 28) was which.

It would have saved all that fussing if the right 0.50 mm terminal had a part number. But overall, I like this mod!

 

Found for $40 at an auto recycler, an 84140-48200 column switch off a 2009 Lexus. That's the stalk with both the auto light position and a fog switch. Drops right in (if 'drop' is quite the right word for fussing with the big springy hose clamp Toyota uses to fasten it!) and looks completely original.

I do have to very slightly walk back my original description of the automatic panel light control. I thought it was taking over the panel dimmer to seamlessly match the panel brightness with the outside. It doesn't, it just has a trip point in the outside brightness where it flips between full daytime panel light, and whatever you've set the panel dimmer to for night. Still nice, just not as nice as I thought.

-Chap

 

Chap,
Do you know if this would have the same functionality? Can't see the details on ebay - I want to have all the parts in place before I start.
09 LEXUS ES350 HEADLAMP SWITCH 84140-48210

 

Well ... different part number, it's hard to say. I held out to find a seller who posted photos of the part.

If I put that part number into Google image search, it looks like that one might have the little joystick attached for Lexus electric tilt/telescope steering.

I guess you could mod motors onto your steering column too ... or think of something else to use the joystick for.

You can tell from the image search that a lot of people mention the same part number when they're selling different things. :/ Or it could be that the image comes from a page showing multiple things, and the part number was for something else on the page. More reason to make sure the seller posts photos.

-Chap

 

has any or does anyone no the pin location is it looking or front same other connectors. maybe already discussed here but my eyes are killing me

 

Hi

I own 2008 Prius gen 2. I install the new stalk . And I bought the light sensor (3 pin) and cable. Can anyone help me? Because Prius gen 3 and gen 2 ECU harness is different.

The light sensor have 3 pin, 1 is connect to 12v, 1 is signal and 1 is ground.
But I don’t know which pin for 12v ground and signal