Looking to make factory fogs work in my 17 LS, need some input

[Ryan212]

The dealer doesn't have the option in their tools to do it, he is correct on that.

I know it can be done, the same BCM controls it just fine on a LT and higher trim trucks. Its just a matter of how much time it will take to figure it out and implement it. I've got 3 different approaches, with one being easy, one being harder and one building a custom module that would connect to the switch and the CAN bus.

 

[Ryan212]

Good and bad news. Good news is the instrument cluster will respond to the bcm to show the fog light indicator as long as the bcm has fog light programming enabled. I was able to program my truck as a LT for this test, bad news is the LT bcm programming makes the rest of the truck upset, theft lock on the radio and warning messages on the dash. There are no options to enable it in programming as expected. Unfortunately even sending the fog light command through gds2 doesnt work without the bcm programming.

 

[Ryan212]

Learned more today. For all of those who were unable to find KR46 fog the fog lamp relay, it is because it is inside the fuse box.
I took my fuse box apart tonight to figure out how the wiring worked internal. There are several relays soldered directly to the circuit board.

I have sourced the correct terminals and have installed a 16awg wire in my fuse box, I have completed the wiring to the fog lights, I just need to get the BCM to allow the fogs to work as desired.

I have isolated the changed between the exterior lighting segment, there are several0x 00 that are changed to 0x01, so I assume that is to enable the fog lighs. I have a spare BCM on order and will take that apart once it gets here. I hope to find some JTAG/BDM connectors to allow me to dump the flash memory and just swap segments until it works.

I will post some pictures tomorrow

 

[Ryan212]

View media item 27289
Checking for continuity from J3 output to the fuse.
View media item 27290Trying to find the fog lamp relay by checking fuse. Unable to find continuity to all of the relay sockets.

View media item 27291Fuse box disassembled, Identified the fog lamp relay, Located near the K6 label in the bottom right section.
View media item 27292Terminal J3 missing as expected.
View media item 27293Removed TPA, added J3 terminal and reassembled.
View media item 27294Reinstalling TPA
View media item 27295Fuse box connectors all put into position, ready for fuse box to be reinstalled.

 

[Ryan212]

Bought a spare bcm, disassembled it, need to figure out who makes the microcontroller. Part number looks to be proprietary.