Special Lighting Hookup

[nermol]

The BCM will set DTCs for both low current (open/bulb out) as well as high current (over loaded/short to ground). The thresholds at which the BCM will set DTCs are dependent on the load being driven. For example, an LED headlamp is going to draw less current than a halogen headlamp.

Thanks for your insights here. I am trying to make sure I understand the system before I decide if/how I would use the highbeam as a trigger on a relay.

I understand the BCM system designer wanting to protect the circuit from over/under load for >1A but are you saying the 150-200mA from a relay coil would cause DTC's to be raised as well?
Are the DTC's only raised after certain number of event thresholds has been reached, or is every event logged? Could you check the status the first time you wired it up and know you are safe?

Thanks again.

 

[FordTechOne]

Thanks for your insights here. I am trying to make sure I understand the system before I decide if/how I would use the highbeam as a trigger on a relay.

I understand the BCM system designer wanting to protect the circuit from over/under load for >1A but are you saying the 150-200mA from a relay coil would cause DTC's to be raised as well?
Are the DTC's only raised after certain number of event thresholds has been reached, or is every event logged? Could you check the status the first time you wired it up and know you are safe?

Thanks again.

The thresholds are not published, but will be different for every load. This is why Ford states that the BCM should never be used to drive anything other than the factory component or a relay in place of that factory component. The conditions under which a DTC may set will vary with temperature and component resistance. If the BCM detects an intermittent low current or high current fault, it may not set a DTC immediately. If the fault remains, a DTC will then set. There will be no visual indication of these DTCs to the driver. If a DTC continuously sets for a predetermined amount of cycles, the BCM will set DTC U3000:49 which permanently disables the output and requires module replacement. Some others on here have used a relay driven by the a high beam circuit and have indicated that they did not get any DTCs, but relay draw will vary depending on type/brand etc. The safest bet is to use a solid state relay, which contain no moving parts and draw very little current.

 

[ChinookDriverJoe]

[mention]FordTechOne [/mention] slightly off topic question. Do the clearance lights on the fender flares operate this way as well (BCM)?
I tapped the passenger one to switch a relay for my LP6 backlighting. No problems so far but after reading this I’m a little worried.


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[FordTechOne]

[mention]FordTechOne [/mention] slightly off topic question. Do the clearance lights on the fender flares operate this way as well (BCM)?
I tapped the passenger one to switch a relay for my LP6 backlighting. No problems so far but after reading this I’m a little worried.

Yes, they are powered directly by the BCM using an FET. A single FET powers the parking lamps, front side clearance lamps, and grille lamps.

 

[Chazzersgarage]

Ok. @FordTechOne I just happened to see your post. Does that mean I'm creating a potential problem running the S8 backlighting off of the marker lights? That's been recommended in the kit.

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[FordTechOne]

Ok. @FordTechOne I just happened to see your post. Does that mean I'm creating a potential problem running the S8 backlighting off of the marker lights? That's been recommended in the kit.

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The BCM may be setting an overcurrent DTC depending on the amperage draw of the lights that you have connected. The BCM is only designed to power the factory LEDs, nothing more; I don't think these aftermarket companies understand the implications of overloading an FET. If you have ForScan, you can check for CMDTCs in the BCM and run a Self-Test to see if any DTCs are setting.

 

[Chazzersgarage]

I think a better solution, to ensure safety for the system, will be to wire accent lights from the S8 into my Amber fog lights and consider them an additional bad weather marker. My fog lights are wired into the upfitter switches.

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[ChinookDriverJoe]

I think a better solution, to ensure safety for the system, will be to wire accent lights from the S8 into my Amber fog lights and consider them an additional bad weather marker. My fog lights are wired into the upfitter switches.

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That’s a great idea


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