Trailer Brakes wiring: 2010 Toyota Sienna

[asavage]

I don't have a tow vehicle set up for electric trailer brakes, and I recently bought a baby dump trailer, so I had to add trailer brake wiring and a controller to my 2010 Sienna. I settled on a used Tekonsha Prodigy P2 via eBay that had been installed in a Honda Pilot and had an adapter harness for that vehicle.

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Last year, I'd removed the receiver hitch and had it media blasted so I could repaint it; the van was from Maine or Connecticut or something and while the van itself has only a light dusting of surface rust underneath, the Curt receiver hitch was rusted quite badly.

After blasting . . . it's still pretty pitted:

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. . . but structurally it remains serviceable.

Now I had to drop it out again, to get a receptacle mounted to the bottom of the bumper. There's no way a receptacle would survive mounted under the cross tube, and precious little space above it.

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So, down it comes (I really should buy the tool to aid in removing the exhaust pipe rubber hanger):

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This needed more bending, which is tricky to do with the tools I have, and made bolts a requirement -- a screwdriver will no longer fit, top nor bottom -- and because one cannot purchase bolts at a hardware store smaller than 1/4", I had to buy metric bolts, SS of course with matching nylock nuts, and I think I settled on M4 or M5:

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More massaging, and it fit:

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As I already had a taillight converter installed for the flat-four pigtail I'd been using the last eight years, I needed to run the lighting part of the harness to the passenger side to graft to the existing converter wiring, but the heavy brake/charge wiring needed to go to the driver's side to run forward. I had purchased a Tekonsha/Draw-Tite 118607 wiring kit which is designed to provide the 7-way blade receptacle, a flat-four plug to use your existing lighting receptacle, one White ground wire, one Red Reverse wire, and a jacketed pair of heavy wires to run forward to the battery and brake controller.

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I discarded 4/5 of that kit but installed the receptacle & wiring. As it happens, my existing flat-four pigtail turned out to be in poor condition due to having been caught in the tailgate latch or something a couple of times over the years . . .

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. . . so I cut it off up at the converter box, and extended the three lighting wires + ground from the new harness, up to the converter, located under the jack. I loomed the wires.

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In order to dress the wires away from the tailpipe, I needed an attachment point and none were handy. I punched a hole in a body seam using a Dremel with a 90° attachment, as I could not fit any of my drills up in the space.

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Then I had a hole through which to run a wire tie.

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I used a utility knife to cut a hole in the rubber body hole plug, and ran the loomed wires up to the jack area.

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Spliced the harness extension to the taillights converter:

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I secured the white ground wire under some random 10mm bolt in this area, and tucked all the wiring under the jack.

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Moving to the driver's side, the LR interior panel must come off.

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My previous splices for the RT & TL (in 2018):

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This support slides up and out:

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I pushed out the rubber body hole plug and cut a hole in it:

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And pulled the harness' pair of jacketed heavy wires through to the interior:

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I nestled the wire along the carpeted edge so it would be behind the plastic interior panel when reinstalled. Removed the plastic sill at the sliding door, the B-pillar, the driver's sill, and driver's kick panel.

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This clamshell at the sliding door had to be un-taped and hinged open so I could route through it; there wasn't a clean way around it.

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Driver's sill removed, plenty of room here:

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Moving to the engine bay, the circuit breakers needed to be installed. I elected to mount the brake and charging breakers to the fuse box's lid.

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These are Blue Sea CBs, with manual resets:

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I Dremeled some plastic off the side of the positive terminal cover:

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Now it got fun.
The Blue (brake) wire needs to route to the controller, the Black (charging) wire through the firewall to the battery, and another wire has to come back from the battery back to the controller. The last two are on separate circuit breakers, so you can't tee under the dash.

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Toyota firewall harness grommets sometimes have an extra rubber nipple, unpopulated, that can be used to route extra accessory wires through, and mine did, phew. I was unable to get a really good picture, and it's a contortion job to put a hand on it, but the nipple can be cut and wires fished though to the engine bay. On this van, the engine bay side of the grommet cannot be visualized at all.

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I routed the jacketed wires from the sill up the A-pillar and behind the parking brake bracket:

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I prepared the wire for fishing by piercing the jacket with an awl, affixing mechanic's wire, taping it smooth, and pushing the wire through the grommet nipple. A bit of lubricant on the jacket certainly helped a lot here.

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Now that the wires were through the firewall, it was time to mount the controller and connect it to the power/trailer brake/ground/brake switch wires. Here's where the controller ends up:

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I started with this harness loop section, routed from/to the firewall grommet.

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I cut off the Honda Pilot adapter portion of the harness I'd received with the used controller, loomed it, and added an M6/1/4" ring terminal for ground. I estimated the length of the harness I'd need from the receptacle in the rear/bottom of the controller, to where I'd connect the wires to the vehicle. There are adapter harnesses that you can buy for some vehicles (like that Pilot), but not for this series of Sienna (though later Siennas: yes).

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I bled on things a bit to assure quality:

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The wire colors are all over the map here. The controller 12v+ is Black but I am bringing it power on Blue because the harness through the firewall's conductors are Black and blue, but in that harness, Black is used for 12v+ back to charge the trailer battery, and the remaining Blue is from the battery to the controller in this case. I could have run two wires of my own color choice through the firewall, but that would have meant an extra splice.

Note that I've heat-shrinked the Blue wire from the battery with a Red sleeve (on both ends) to indicate I've repurposed it.

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Connecting the controller to the brake switch. A couple of different ways of looking at it. This first diagram looks confusing, but that's because it covers (has wiring shown for) vehicles both with and without optional Dynamic Laser Cruise Control, so in reality you choose one or the other and it simplifies. OTOH, that first diagram shows the Stop Light SW but only half of it: terminals 1 & 2 (of four), lol. The second diagram ("testing") shows all four terminals. Anyway, the wire I need to tap is G-W:

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While it's possible to tap this as-is, there's not a lot of wire length to work with that way. I de-pinned the G-W wire from the connector. The white side lock has to be pried out a bit, then depress a plastic tab to release the terminal from the housing.

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Then I used a utility knife to strip some insulation, soldered a tap wire in and taped the junction, then spliced that White tap wire to the controller harness' Red wire. Yeah, the controller harness colors are Black = 12v+, Red = Brake Switch, Blue = Brakes, White = Ground [shakes head].

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I found an appropriate location to ground the controller:

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Tucking and restraining the various bits:

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I could then connect the power at the CBs:

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Mounting the controller to the knee bolster was a bit tricky, but only in choosing where the holes go. One of the few times I've not regretting having some factory option:

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The rest was cleanup and setup. The left kick panel was missing the plastic threaded nut and a clip that fell inside the body I guess.

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90467-06147 $1.89

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90467-09204 $1.65

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Those were $12 to ship, and no cheaper at the local dealer.

This all took me about . . . a week to get done, at my pace.

[Nissan_Ranger]

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Gah! You have SO much more patience than I do. After almost 50 years of wrenching, I hate working on my stuff... A few weeks ago, I finally tackled the job of repairing a fuel pressure leak on the top of my chev halfton fuel tank. It was rotted with rust. and I had to get at it. So I cut a hole in the truck box to get at it. Lots of rust and holes. Replacement unit is over $800.00 and that was just not happening. Out came the cyanoacrylate (Crazy Glue) and fiberglass cloth. Can't use epoxy because it won't stick to rust.
About 4 hours later, success with the leak and holes. I welded flanges on the piece I cut out of the box, drilled holes, and re-attached it. Box liner put back in and DONE!

[asavage]

I wouldn't know how to begin working in an environment with the snow-melt accelerators you folks use. It's an entirely different mindset.

I've been trying to give away the '83 Maxima Diesel Sedan that I sold Mark in 2007 and has been sitting for around five years in his mother's driveway, and no interest around here. I suppose I'll have to haul a battery over there (which is expensive due to the ferry involved, and summer surcharge, and that route requires reservations both coming & going) and get it running and make a video.

That was the only way to get rid of his '77 300D earlier this year: nobody would literally take it away, complete car that hadn't run since '13. After probably (50) people wanted it but failed to actually take it, I took a battery to it and fired it up in under five minutes, took a 45-second video, and posted it to FBM. Sold it for $350 in three days.

But what we here consider "rust" is nothing on you folks. I occasionally watch YT vids from east coast auto repair shops and the rust is unbelievable to me. I've got that 54-year-old '73 F600 in front of my house, that I bought for the crawlspace deepening project that basically has "no" rust and original paint, and it's probably sat outside its entire life -- certainly the fellow I bought it from didn't garage it, and neither have I since Feb2024. But this area didn't salt the roads here until 2008, and even now we get so little ice & snow that they don't use all that much around here . . . nothing like you folks, I imagine.