I have it trouble shot down to the relay. What tells the relay to close the gate to send power to the headlights? When I jumper the relay the headlights come on and work.

The relay is good

 

Simply put, the headlight switch and the daylight sensor tell the BCM to turn the headlights on and the BCM activates the relay.
Here's the detailed description from the shop manual:

Exterior Lighting Systems Description and Operation

High Intensity Discharge (HID) Low Beam Headlamps
The headlamps may be turned ON in 2 different ways:

• When the headlamp switch is placed in the ON position, for normal operation

• When the headlamp switch is placed in the AUTO position, for automatic lamp control (ALC)

Battery voltage is applied at all times to the coil and switched side of the low beam relay. Ground is applied at all times from G201 to the turn signal/multifunction switch. When the turn signal/multifunction switch is placed in the HEAD position, ground is applied from the turn signal/multifunction switch through the headlamps ON signal circuit to the body control module (BCM). The BCM applies ground to the headlamp low beam relay control circuit. This energizes the low beam relay, closing the switched side and applies battery voltage to the LEFT and RIGHT LOW BEAM fuses. Battery voltage is then applied from the fuses, through the low beam voltage supply circuits to the ballast in the headlamp assembly. When battery voltage is applied to the headlamp ballast through the low beam voltage supply circuits, the ballast charge the starter to start the lamp. High intensity discharge (HID) headlamps do not have filaments like traditional bulbs, instead the starter uses a high voltage transformer to convert the input voltage into a higher voltage. This increased voltage is used in order to create an arc between the electrodes in the bulb.

Ground is applied from G101 for the left headlamp and G102 for the right headlamp.

Hope this helps, let us know what you find.

 

Would anyone happen to have the wiring schematic for the interior blinker headlight switch? I would like to jumper it and see if its my actual problem. I'm down to the BCM or blinker/light switch, but if my daylight sensor is not activating them either sound like a BCM issue.

 

Here's a screen shot from the shop manual.

 

Thank you.. I'll rip into it tomorrow.

 

So update to this I changed out the multi function switch, double checked grounds G201 and the 2 in the frame rail G101 and G102 with no luck. So I then decided to take voltage readings when I turn the headlights on and off.

The results where when I turn the headlights on its only a 9volt signal to fire the headlights.

This explains why I jumper from the hot at all times 12volt lead they work.

What would cause only a 9 Volt signal from the BCM to fire the headlights? Its not enough to make them fire.

 

Worse case is that it could be a bad BCM. I've attached the 2007 exterior light section that troubleshoots the circuit with a jumper.
It should be the same for you car as well.

Good Luck, and report back if you figure it out.

 

Thank you, let me dig through this..

 

A low voltage reading in a situation like yours means that there is voltage loss somewhere prior to the point where you are taking your voltage reading. In most cases, this is caused by dirty or corroded connections.

 

12v is supplied to the relay coil and switched side at all times by the battery, not the BCM. The BCM grounds the relay coil to trigger the switched side. So if the relay is working OK, the BCM and headlight switch are OK.

When the relay triggers, 12v is sent first to the fuses, then to the headlight ballasts.

Where are you measuring 9v? Look upstream from there to find 12v. In between will be the problem. Once you find it, it will be obvious. Good luck!

 

K3 which has power on it full time is 12volts, K2 which is operated from the multi switch is where i got my 9volts from. Mind boggling I'm at a loss where to go next with this, it does have a new fuse block. I changed that out in the beginning thinking that was it originally.

So what in the world is between K3 and K2 ? I assume a single connection wire?

 



 

Yeah, k2,k3,f1&f2 should all be 12v. If not, maybe there's a problem at the splice where the wires join together? Or the wire leading to k2? Or the k2 relay socket? Could it be the wire inside the fuse box that was the cause of the headlight recall?

Let's back up a bit. You said in the first post that when you "jumper the relay" (bypass?) the headlights work. Did you try another known good relay?

 

Yes, that is the first thing I did was get a new relay. I have also swapped it with others no luck. The headlight recall??? I will pull the fuse box again and check that thoroughly. I did see it when I pulled it the first time when I replaced the fuse box.

 

Sorry, I'm out of ideas without seeing the car. This is a tough one for sure. Hang in there, you'll find it, and please let everyone know what the problem was when you fix it.

 

There is a recall for the low beam headlights. They fail to work caused by a break on the ground wire under the fuse box layer. Most times, the headlight doesn't work only when the engine bay gets hot. This causes the solid ground wire to expand where it is broken, and cuts off the power to the low beams



This may not be the issue, but if everything else has been tried and nothing found, might be a last resort.
I'm assuming that your high beams work. These are on a separate circuit.
I've attached a PDF from a member that took his fuse box apart, found and fixed the issue without needing the recall.

 

I put a brand new fuse box in it, no results.

 

Did this to mine a week ago, didn't have any issues but wanted to be pre-emptive. I think the price of the parts was around $6.00.

RCRIT-14V251-2256.pdf (nhtsa.gov)

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Thank you, the jumper on mine is only 1 wire. Not pig tailed like that one with 2.