Hello,

long story short; I installed the ford bed lighting kit on my 2018 ford f150 5.0l 4x4 with the 300a options package and it doesn’t work because the 300a doesn’t support that (in the fine print on the ford kit details - I missed that when I bought it). See my original thread on how we figured that out. (Bed lighting does not work)

while I’m working on a workaround I’m wondering if any of the brains on this forum would know why the 300a doesn’t have power on port 44 on the bcm? What ‘feature’ isn’t in 300a that is needed to enable it?
there is information out there that its associated with the cargo light circuit and that works fine so that’s not it. Could it be I need electronic seats?

I’m hoping there is a feature I can enable using forscan to get it working. (Enabling a feature not physically installed my cause other issues but I’ll deal with that when I find out what it is)

appreciate any insight.

 

The Bed Lamps are powered by the BCM White Light FET. The Cargo Lamps are powered by the BCM Puddle Lamp FET. The only thing that is shared between the two systems in the switch circuit. It is most likely that the BCM for the 300A does not include the White Light FET and therefore the lights won't work the way they are intended to. There are many different versions of the BCM for the various different option levels.

You could get around this problem by powering the Bed Lamps from the Puddle Lamp FET. If your truck does not actually have Puddle Lamps then adding the Bed Lamps to the circuit likely would not overload the FET and trip the circuit. If it does, then you may need to add a relay to the circuit. Use the Puddle Lamp FET to switch the solenoid and get the power for the Bed Lamps from a Hot at All Times BCM fuse using an Add-a-Fuse or adding a circuit to one of the unused BCM fuses (more complicated but cleaner). This would make the Bed Lamps work, but, unlike factory installed, would turn them on every time the Cargo Lamps come on, such as when you open a door.

Here is the electrical schematic for the bed lights for MY2018.



Here is the electrical schematic for the Cargo Lamps for a MY2018.

 

I guess gone are the days I could read wiring schematics.
Looking at the top diagram, it looks like the bed lights get their power from that BCM. But there is no switch between it and the bedlamps. I realize that many circuits are now completed by closing in on a ground, but it appears the bedlamps would be on full time since there is nothing but the lamps between the BCM and ground.
I don't know what a white light FET is.

 

You are correct, there is no switch on the Bed Lamp circuit. The BCM monitors the Bed Lamp and Cargo Lamp Switch circuit for a ground. When you press the switch, it momentarily grounds the circuit, which the BCM sees. The BCM, via a microprocessor, turns the output of the White Light FET (Field Effect Transistor) and Puddle Lamp FET circuits on to power those circuits. If you press the switch again, the BCM sees the ground again, and knows to shut the circiuit off. If you just wait without pressing the switch again, the BCM times the circuit and shuts it off when it has timed out.

Each FET in the BCM powers different functions and the FETS are microprocessor controlled. For example, when you open a door, the BCM sees the door open, via the door ajar switch. The BCM then turns the Courtesy Lamps and the Cargo Lamps on by turning on the ouput of the appropriate Interior Lamp and Puddle Lamp FETs. The BCM then shuts those circuits off after a set time after the door is closed. If you don't close the door, the BCM uses a different longer timer to finally shutdown the circuits.

The various microprocessors that controls the FETs also monitors the circuit amperage. Each FET has a maximum allowed current based on what the circuit operates. If the FET sees an over-current, it shuts the circuit off to protect it. The FET auto-resets on the next ignition cycle (Off/On). If the FET is over-current tripped too many times, the circuit remains shut off, a DTC is set in the BCM. The circuit remains off until the problem is corrected, and the DTC cleared with a scan tool. The BCM monitors the number of times a FET is over-current tripped. If a maximum number is achieved (it is in the hundreds) the circuit is permanently disabled and the BCM must be replaced before that circuit will work again.

Nothing is simple anymore.

 

Thanks, I'm gonna have to read that a couple times, but I think I get the gist of it.
Now, I'm sorta leery about grabbing power from my existing bed lamps. I have a set of LED lights I was going to wire in using the bedlamps supply, positive, and then just run a ground for them.
Oh man, you're so right, nothing is simple anymore. Thank the Lord no one has tampered with residential wiring, there isn't any magic there!

 

Wow, this is fantastic @52merc; much appreciated. I also have the entire schematics (mitchel1 account) and was looking into workarounds but yours will work just fine.
I don’t have puddle lights so I’m golden.
And, thanks for the explanation on the 300a bcm vs other packages. Makes perfect sense.

 

You can try to tap into the circuit. The worst that will happen is it trips the FET. It all depends on the current draw of the LEDs you are adding. BTW, if you let it trip enough to set the DTC, you will need a scan tool or FORScan to clear the code. It will not clear itself.

If it does trip the FET, then you will need to use a relay and get addition power from somewhere else. If it were me, and that happened, I would just stay with the OE lights.

 

so, a couple of questions.
- is the above powering the bed lights from the puddle light circuit then or is that circuit just a switch to turn on the lights (which are powered from an always on circuit)
- the switch in the box does nothing then and you need to turn on the box lights using the cargo light switch (or open the door)?

Im not quite clear on how the trigger fits into this. I understood how the bed lighting switch created ground in the bcm which then released power on the port 44 but I’m not following what the puddle lamp fet triggers the power (which is always on)?

maybe it’s because it’s Sunday night but this isn’t connecting any neurons

 

Don't confuse the switch circuit with the lamp powering circuits. They are not physically connected. If you power the bed lamps from the puddle lamp circuit everything will work the way you expect except for one minor thing. When you press the cargo switch, the cargo lamps and the bed lamps will illuminate. When you press the switch again, they will shut off. If you press the bed lamp switch in the bed, the cargo lamps and bed lamps will illuminate. If you press the bed switch again, the lights will all go off. The only thing that will be different from OE is, when you open the door, the cargo lamps and the bed lamps will illuminate. Normally, in factory installed bed lamps, only the cargo lamps illuminate when the door is opened. In your case, the bad lamps will illuminate as well. That is because you are powering it from the puddle lamp circuit.

The puddle lamp circuit is not always on. It is only on when you open a door, press the cargo switch, and when you press the bed lamp switch (in the bed). Your BCM dosen't physically have the White Light FET, and therefore, can't provide any power to connector C2280B Pin-44 (what you are calling port 44). The bed lamp switch and the cargo lamp switch are in the same circuit and either one turns both the bed lamps and the cargo lamps on at the same time.

On my F150, with factory installed bed lamps, the following happens:

• When I open any door, the puddle lamps (my truck has them) and cargo lamps illuminate. The bed lamps do not illuminate. The lights go off when I close the door.
• When I press the cargo lamp switch, the puddle lamps, cargo lamps, and bed lamps all illuminate. Pressing either the cargo lamp or bed lamp switch makes the lights go off.
• When I press the bed lamp switch, the puddle lamps, cargo lamps, and bed lamps all illuminate. Pressing either switch turns the light off.
• If you don't close the door or press either switch a second time, the puddle lamps, cargo lamps, and bed lamps stay illuminated until they timeout and shut off.

I hope this helps you understand all this.

 

Ok, I read this a few times and I think I got it. The part that was confusing me was your comment above "Use the Puddle Lamp FET to switch the solenoid and get the power for the Bed Lamps from a Hot at All Times BCM fuse using an Add-a-Fuse or adding a circuit to one of the unused BCM fuses (more complicated but cleaner)".

So, all I need to do is tap into the white/green wire coming out of the BCM at pin 26 (at some point between the BCM and the cargo lights) and run it to the back and then have it replace the current wire going into Connector C411 pin 14. That pin is the one that powers the bed lights from the readily accessible connector underneath the truck.

Sound right?