Fog Light circuit amperage?

Dogdad

Tremor Buff
Joined
Sep 6, 2021
Messages
75
Reaction Points
189
Location
Tulsa, OK
Current Ride
2022 Lariat Tremor, 6.7 PSD; Stock-ish
Current Ride #2
2001 Excursion 4x4, 7.3 PSD; Lots of mods
I never use fog lights for fog. I've always upgraded them to off road lights. With bambi mode now available, I'd like to replace the factory halogen fogs with some off road lights.
I've looked at fuse-box diagrams for a fuse, but it appears that they are wired directly to a computer. Body Control Module maybe?
Blowing up a fuse doesn't scare me, blowing up a computer does.

Does anyone know how much power the fog circuit can handle?

Thanks.
 
well-waiting.gif
 
Last edited:
Fog Lamps

System Diagram


imagen2.dll

Network Message Chart

BCM Network Input Messages



Broadcast MessageOriginating ModuleMessage Purpose
Headlamp high beam status SCCMIndicates to the BCM a request for the high beams and then disables the BCM fog lamp output while in high beams mode.
Headlamp flash to pass status SCCMIndicates to the BCM a request for the flash-to-pass and then disables the BCM fog lamp output while in flash-to-pass mode.


Fog Lamps

The BCM monitors the headlamp switch position by sending voltage signals on multiple circuits to the headlamp switch. There is one circuit for each headlamp switch position. At any given time, one of the signal circuits is switched to ground to indicate the headlamp switch position.

When the BCM receives input from the headlamp switch indicating a request for the front fog lamps, the BCM provides voltage to the front fog lamps.

When the SCCM reads a flash-to-pass or high beam request from the LH steering column multifunction switch, the SCCM sends a message over the HS-CAN2 to the GWM, then the GWM sends the message to the BCM over the HS-CAN1. The BCM disables the fog lamp output while in flash-to-pass or high beams mode

If equipped, when the vehicle is in snow plow mode, the fog lamps are disabled.

The BCM also provides Field Effect Transistor (FET) protection of the rear fog lamp output circuit. When an excessive current draw is detected, the BCM disables the front fog lamp output circuit driver.
Refer to: Body Control Module (BCM) - System Operation and Component Description (419-10 Multifunction Electronic Modules, Description and Operation).
 
I

The setup I want to run will pull just under 12 amps per side at 12V.
A normal halogen bulb would pull 3 to 4 amps so triple the load. I would say you would need to run that through your upfitter switches, or its own wired circuit
 
So I checked the two 40 amp fuses and I have no power going to either one of my fog lights ... But the switch says it on ... Is the computer now doesn't want to turn the lights on that has no issues for 10 months
 
Try disconnecting the lights and check voltage , maybe one of the light has a dead short. If I understand it the bcm will protect it's self if there is a short and just not activate the circuit.
Yep done that... No power
 
the 40 amp fuses are for the entire BCM not just fog lights , If you draw more the what the truck thinks the lights should draw they will shut down to protect the BCM. my fog light require an input from the main light switch to activate so that you have some kind of rear lighting too
 
the 40 amp fuses are for the entire BCM not just fog lights , If you draw more the what the truck thinks the lights should draw they will shut down to protect the BCM. my fog light require an input from the main light switch to activate so that you have some kind of rear lighting too
So I have completed unplugged the fog lights and still get no power to the positive wire
 
Back
Top