I checked the lamp bulbs in rear hatch and both appear to be good. I did not actually pull the panel and disconnect the harness to full test the theory but I pulled the lamps and checked the bulbs. I also manually operated all the internal lamps and the work with the buttons near the lamp.
So I’m sitting in the car now.. I have pulled the overhead dome console and I’m testing with lamp for power. I have power coming into lamp on purple w/wht, red w/wht, gray, orange. I do not show any power coming from the gray w/blk. If BCM is sending signal should I see power on this Gray/Blk wire?
Ok.. so if I don’t have any power on the gray w/blk coming into the overhead panel do you feel it’s likely the BCM that is not working? I also pulled the headlight switch and I have the purple w/wht that has power and the green appears to be for the dimmer and will have power when turned to on. I do not have any power to the pink w/blk in the switch.
Check to see if the Grey/Blk is grounded. I suspect a short to ground. I would be nice if you could access all the connectors and disconnect them one by one. I would hate to see you go through the expense of buying it, programming it and not have this PITA solved. And if there is a short, it may or may not cause the BCM dimming feature to go bad, but if you still have a short, it may, (or may not) cause the new BCM to go bad. Sounds like the issue that Tynee had, was possibly a bad bulb caused a low resistance to ground and caused his issue, it looks as though his BCM recovered. I don't believe that two burned out bulbs caused his to go and miraculously cure itself with a new bulb, I believe something else was disturbing the wiring inside the Liftgate. I know that I get water in mine, droplets come out of the interior rubber membrane closing switch.
If you can take off the connector for the lights, the one with GR /BK, at the BCM. First check for a short to ground, Take a wire from the positive source, with a separate inline testing fuse, say 5 amp, and jumper it to that GR/BK # 690 wire and see if the lights come on or if the fuse blows.
Ok... so if I’m following you correctly you are suggesting a run a wire day from the positive post of the battery and touch to the gray w/blk wire coming from the BCM. You are suggesting on the wire that between the battery and the gray/blk to just put a 5amp fuse to protect the components on that wire. I guess we would just be running a bypass of the BCM? If I’m following you correctly this sounds like a great idea...
Happy Memorial Day. Ok.. I tested first thing this morning and here’s what I did and what happened. I ran a wire from the fuse box under the hood. I have a handful of fuse taps so it was just easier to tap there. I pulled down the BCM but kept everything fully connected. I found the gray/blk wire in one of the wire blocks. I then pulled the overhead dome panel and checked continuity from that wire in BCM to the gray/blk in overhead panel to make sure it’s the correct wire. I then left the wire plugged into BCM but touched my 12V tap wire to the gray/blk from the back of plug going into the BCM. When I did this the fuse would immediate blow. I did not test by first pulling the plug from the BCM and touching the 12v tap wire to gray/blk going to overhead panel because there are so many other wires on that plug that I felt should likely be plugged during test... but I’m really not sure. I guess I expect that if I put power directly to the gray/blk that has continuity with the overhead panel that would light up... so wondering if given the manner that I tested by keeping plug in BCM is correct and if the fuse blowing would indicate a short to ground?
Yes, but he is also reading the resistance of the bulbs in the connectors to ground. I just checked mine at the rear hatch.
Both hatch bulbs in = .8 ohms to ground
One hatch bulb in = 1.1 ohms
Neither hatch bulb in = 1.4 ohms all on gry/blk wire to gnd.
My bulb in the rear may be different from yours. are yours miniature or a long tube with the connections on each end?
I calculate the current with just the 6 map lights would be 2.4 amps, we would need to figure in a higher current and different resistance if yours had the longer bulbs.
These are what my rear hatch bulbs look like. I believe they are a different wattage than my maps lights, but same design.