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#1
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Third Brake Light issue
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#2
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Codes?
That'll tell you usually if there's a fault before the light or because of it. Sent from my SM-A730F using Tapatalk
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"When the Team Chief said.... You're trapped in a hole with nothing but a goat and a slinky, what do you do? Stubby said, I'm not sure but it won't end well for the goat...." ~(Overheard) Last day, Phase 3, Q Course |
#3
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I had some problems with a couple of segments in my LED 3rd brake light bar in my 2001 3.0i. I fixed that by reflowing the solder on the LEDs. The individual lights are in 6 segments of 4 LEDs each.
The light bar assembly is powered with 12V at the Blue + Brown wires. So with the light bar removed / disconnected, stepping on the brake, you should be getting 12V at those wires. If not, the problem is upstream of that point. The bar is wired internally so each of the 6 4-LED segments gets its own 12V, which then drops across all 4 LEDs in series. So if you have any single LED or solder joint failure, you are likely to lose the whole 4-LED segment, or 1/6th of the light bar. Minor failures like that did not cause codes for me.
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2001 X5 3.0i, 203k miles, AT, owned since 2014 |
#4
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Yeah, that’s my problem. No power at the plug in the spoiler. So trying to find out where the disconnect is at. Do the blue + brown wires come off the taillight assembly in the rear? If so, I might just run new wires from that point up to the third brake light.
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#5
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I don't know where that 12V on those two wires comes from, since I never needed to trace that back. So my story is just to confirm that those wires are simply 12V when the brakes are on, and 0V otherwise. Nothing weird due to the LED, vs. the other lights which are all non-LED (on my car at least).
If you can't find someone else with the answer, or an accurate wiring diagram ... If you find a blue+brown pair of wires further upstream, you might assume they should be 12V / 0V for testing purposes, and go from there. Too bad you bought an unneeded light bar. Those things were close to $200 when I had my issues, which is why I went for the repair vs. replace option. The repair is holding up solidly after solder reflowing.
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2001 X5 3.0i, 203k miles, AT, owned since 2014 |
#6
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Are you familiar with the online TIS website? You can look up the wiring schematics: https://www.newtis.info/tisv2/a/en/
Enter the last 7 digits of your VIN...then type some keywords or phrase into the search box to see if you get any results that might lead you to the wiring diagram for the high mount brake light. Or you can try to find it on your own perusing through the wiring diagrams and functional description link. EDIT: click link and look for H34 (raised brake light): https://www.newtis.info/tisv2/a/en/e...centre/hKBHqmp
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Last edited by Qsilver7; 05-16-2019 at 03:24 PM. |
#7
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Great links, Qsilver7...
It looks like the positive power to the third brake light connector (X138) is a single continuous wire, right back to the LCM. My next test would be to check if there is power between the black/yellow wire (X138, pin 2) and a known good earth point, as the issue may be with the earth connection rather than the power connection (as the earth connection has more joints). Clearly, you need to test this with the foot brake applied!
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Wayne 2005 BMW X5 3.0d (b 02/05) 2001 BMW F650GS Dakar (b 06/01) |
#8
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Thanks for the info guys. Since I don’t have a garage to use at the moment, I have to wait until the weather clears up in order to tear into this again
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#9
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update
I still haven't been able to track down the problem with my third brake light (high mount, center in the spoiler.) I have a Foxwell NT510 scanner, and it shows no issues with the LCM or brake lights. No fault codes. Brake switch controller checks out ok, too. When I ran the live tests through the scanner, it tells me the third brake light is activated, even though it's not lighting up. Just to make sure, I did a live test on all the other lights, and they all work correctly. And to double check, I disconnected the third brake light from it's connector in the spoiler and hooked it up directly to a different power source, and the LED's came on. So I know it's not an issue with the LED's or the unit itself. If there is a break in the wires somewhere coming from the LCM, wouldn't I be getting a fault code on the scanner? Just wondering what my next step should be.
2003 X5 4.4i, 6/03 build date Last edited by Bradleylee; 07-01-2019 at 12:35 PM. Reason: add signature line |
#10
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Check the wiring in the rubber boot that goes from vehicle body to hatch. Very common for fraying and breaks in the wiring at that locale.
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2005 X5 4.4i Build 04/05 Maintenance/Build Log Nav, Pano, Sport (Purchased 06/14 w/ 109,000 miles) (Sold 8/15 w/121,000 miles) 2006 X5 4.8is Build 11/05 Maintenance/Build Log Nav, DSP, Pano, Running Boards, OEM Tow Hitch, Cold Weather Pckg (Purchased 08/15 w/ 90,500 miles) 2010 X5 35d Build 02/10 Nav, HiFi, 6 DVD, Sports Pckg, Cold Weather Pckg, HUD, CAS, Running Boards, Leather Dash, PDC, Pano (Purchased 03/17 w/ 136,120 miles) |
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