Relocating the BSM to Tail Lights

Edit: It works! I moved the sensors to the reverse light buckets and tested it out. Works like a charm! Needs additional testing to be sure it doesn't consistently throw error codes, but so far no techstream is needed after relocation that I can tell.

Pictures of the tail light design on pg3 of this thread

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Hey y'all,

Just as the title states, I'm working on trying to relocate the BSM to bottom portion of the tail lights. The plan is to get a steel rear in the near future, and I'd like to keep the sensors on if for nothing other than the challenge of doing so. I do like cross traffic when I'm backing up as well tbh. I'm well aware of how finnicky the sensors are, what they will/won't "see" through blah blah blah. First hurdle is getting them connected in a new location.

SO, to make them work, gotta extend the connectors so they reach the rear of the tail lights. I bought some OEM TSS connectors to make some pigtails, here's a couple shots, they fit perfectly and I matched the terminals up with each side (which have different amounts of terminals/terminal locations) but it's giving me nothing when I power it up.

Troubleshooting:

Used 20ga wiring and tin connections, crimped and triple checked correct slot locations.
Powered up as expected with sensors connected to stock harness, no issues.
Tried to power up with just drivers' extension installed, did not power up.
Tried powering up with just passenger extension, did power up, but threw an error.



If I didn't get the tin terminals installed just right that'd be the next thing to verify I guess, or to just cut the actual connector wires themselves and solder in extensions that way...but that's a bit more committal to the idea than I want to be just yet. I'd love to make sure that it'll work before I take the plunge and jack up my OEM wiring. Anyways, anyone have anything they could add to this? I'd love to crack this cookie.

 

Here’s the BSM calibration procedure. It might help you get things working once you get the wiring figured out.

 

I'll check that out, thanks for the tip! I was just checking out a BSM TSB that suggests testing terminal voltage to make sure it's in the right range so I might end up having to do that as well. I don't think wire gauge would affect voltage but could be a possibility.

For now I think it's verify the terminals are connecting correctly and installed properly.

 

Upon further reading, the passenger sensor is a slave to the driver sensor which is the master (hence 9 terminals on the driver vs 7 on passenger). So that's the reason for the error when driver is plugged into the stock harness: the master is working but the harness to the slave is not (I promise that's the actual technical terminology). So it sounds like both the pigtails are just shitty. I'm thinking that it's definitely a user error on my part when assembling the pigtails, they're deceptively difficult to get the terminals installed correctly due to how deep seated they are. Annoying. But luckily Ballenger motorsports, who sells the connecters, also sells them preassembled. So I guess I'll have to have the pros do it and spend a little extra dough. Again.

Is it really a mod if it's not actually a money pit in disguise? Oh well. More updates once I have the new pigtails from Ballenger and have a chance to test them out. Assuming those work then we can move on to actual mounting of the sensors which should be more straightforward and fun. The CAD design for the tail lights is already done, I'd love to get those printed out but best to be patient. It gon be good

 

Got the extensions to work, turns out I'm just bad at assembling terminals I guess. On to the next step which is mounting and more testing. It's going to be mounted behind a few mm of clear plastic covered in black vinyl (basically just the bottom third of the tail light lens) so I'm pretty confident that it'll be able to send the signal through that.

 

I had the same thought until I found a steel rear bumper that retained the BSM.

 

Yup, the inspiration. Ford showing the way, just like so many amber grille lights. I might try to have the vinyl say something similar with TSS just to be extra cheeky

I haven't been a fan of the look of BSM steel bumpers tbh, I know Apogee is developing one that looks pretty good but the corners still bulge out like C4's short lived one did. There's no real way to avoid that though, they're not small sensors. I like the look of CBI's rear with swing out, but the latch is a little concerning since it might block the sensors in the tail light.

 

The BSM is to put it basically like a radar system that uses frequencies similar to your wifi router. (millimetre wavelengths)

The reflection of the electromagnetic waves is interpreted by either the master (drivers side) or slave sender/receivers in the rear corners of the bumper.

If the slave detects a strong enough or strong and moving enough signal it sends a pulse to the master that then sends a canbus signal to the body computer that then beeps and flashes.

Metals are great for reflecting back electromagnetic (radio/radar) signals.

So having metal in front of the send/rec unit is just like shining a flashlight in your eyes.

Having metal that is grounded to the same source, will absorb electromagnetic waves and not reflect them back.

The Toyota BSMs also are programmed to ignore the reflection from the floor/road.

The are calibrated with a little metal 2-3" "pyramid" / target on a stand about 12-18" off the ground and 3 meters back from the corner of the truck.

They are also programmed that if they cannot sense the "floor" or there is too much reflection constantly (think of dirt and gravel between the outer facia and the sensor) they will error out also.

Plastics with no metal fillers in it has not great effect on these wavelengths.
(note carbon black and carbon fibre is conductive and does affect/interfere with these wavlengths)

(That is probably why the dark tinted aftermarket front pro sensor covers don't work for a lot of people, too much carbon black in them to tint them dark)

 

Definitely interested if you’re able to get this working. I’ve been holding off on a metal bumper for the same reasons. I’ve only found on bumper manufacture that is compatible with BSM

 

Big kudos to you for trying this! This has been something I hoped someone would try for a long time. Allegedly someone relocated theirs into the walls of their fiberglass camper shell with success but I never saw any actual proof of that.

I've got nothing of real value to add other than if you figure this out and manage to make a kit, sign me up! Oh, and I have experienced a BSM error in the past after one of the sensors got a bunch of mud on it, and after cleaning it off it took driving it around for about 15 minutes before the error cleared and it working properly. Just something to keep in the back of your mind as you continue your R&D work.

 

Interested in this as well. I have a HC rear tube bumper an had to delete my BSM, would be cool if I could add it back.

 

Hopefully I can get it to work. It's at about a 40degree angle from the rear of the truck, and it might be good to angle it down a couple degrees to compensate for the height increase. The next hurdles are the points where the taillights mount to the truck since those will be blocked by the sensor. I'm thinking I'll have to relocate those which shouldn't be too crazy to do but not really excited about the idea of drilling into the sheet metal.



The reverse light bucket is the perfect size for the sensor though. I've got my CAD design the for tail lights finalized to use just the top 2/3 of the tail light. I think I'll gut the reflector bucket and try to fit without modifying the mounts and cover the rear of the lens with black vinyl and use some gasket maker to seal the bottom of the tail light. If not then they'll need to be moved like in my rough sketch.

 

You have my attention if you pull this off. I'd love a metal bumper but prefer the added safety of the BSM, and the Apogee offering sticks out too much like you said.

 

@Puppypunter FYI, maybe he can help?

 

I feel like you don't need to angle them down, and maybe shouldn't. Unless they're something very short in your blindspot! I think the angle outwards is the more important thing to try to keep relatively close, but hopefully that could be recalibrated as well.

 

I would agree with this, I think potentially they might need to be pointed up instead of down to prevent registering the bumper as a foreign object. I would build a bracket to hold and test the sensor with the taillight removed before drilling out the taillights.

 

Fair points, I think they'll be clear of the bumper so long as it's below them. It'll be a bit of trial and error for sure, and I think the bracket idea is good. I may just try bending/cutting a thin aluminum bar and drilling some holes for bolts to have a rough idea. That should give enough play to be able to fudge the angles as needed. Only problem is I don't currently have a steel bumper so it'll probably be a bit before we're sure that it'll work with one Also I'll kinda need to drive around for the BSM to work and test, but not exactly sure how to do that without the local PD getting up my ass especially since I live like 2 blocks from the station lol

And don't worry about the tail lights, I've got a few spares sitting around as I've been going through a few tail light designs before finally landing on this idea

 

If you need any help w/solid modeling or 3D printed parts or simple machined components let me know! I'd love to be able to help and am super interested in this project but don't really have the time or ambition to take it on myself. I also have a good friend who is a radar engineer in case there's anything needed on that front.