Headlight circuit

[hileriotech]

So I was having trouble with the headlights on my Infiniti Q45. Apparently when I try to put the lights on they will not come on. They will only come on if I have the switch in the "Auto" position. I began troubleshooting the circuit. What I found was that they relay was in good working condition, however while checking voltage incoming to the relay I found that I had voltage at both sides of the coil. I know this to be a fault. I should only have voltage to one side and ground on the other. Am I correct.? If any one out there knows what the problem is please fill me in on this. I think this means that my BCM is bad. However, I am not sure of this diagnosis. I would greatly appreciate any and all help. Thanks and thanks for taking the time to read my post. Sincerely Yours, Q45 Troube...

[Q451990]

Welcome to NICO! I would unplug the relay from the circuit and check the inputs again. I got fooled on voltage backfeeding through a circuit while I was checking a contactor in an air conditioner last summer. I'm guessing that if you've gotten this far, you already have the factory service manual - but if not I would follow the diagnostic steps in there. It's available at www.infinitiservicemanual.com

[hileriotech]

Thanks, I have done that many of times. Once again, when I am in the "Auto" mode the lights come on. Thankfully when it is dark is when I need them, obviously. I have checked the inputs over and over again. I tried the inputs at night when the lights are in "Auto". I get the correct readings. but when I turn the switch to the "On" position is when I get this back feed of voltage. Would this be the Body Control Module. Also, where is it located on the 2004 infiniti Q45? Thanks and thanks for taking the time to read this.

[Q451990]

Sadly, I have no experience with that version of the Q45. Hopefully someone will come along with something helpful.

[justcallmewils]

If you're able to figure out what needs replaced, I have a full parts car and can pull whatever you need. Just let me know.

[hileriotech]

Do you have the Body Control Module and how would we make this happen.? I need a few things. ABS Pump, and body control Module..., and also the glove box key/lock handle assembly. Please let me know how to proceed. thanks

[hileriotech]

I have found that both sides of the input to the coil have voltage while ignition key is in on position and with key out vehicle off I have 12v one side and 1.8 ghost volts on other. My gut says this is a bad BCM, just not sure of it. Any help out there??