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When I step on the brakes in my 2010 Toyota 4Runner, I do not get any DC voltage to the "electric brakes" pin of the 7-pin trailer socket (factory installed). (I measure this by touching the probes on my multimeter to the "electric brakes" pin and the "neutral/-" pin at the same time while the brake pedal is fully depressed.)

Every other trailer socket pin produces voltage as expected (i.e. 12V/+, running lights, left light, right light; admittedly I did not test reverse lights). Note that the brake lights do work, but of course that's just the left and right lights powered at the same time.

I pulled and checked every fuse under the hood and in the driver foot well, triple-checking any associated with "towing" or "trailer". I also confirmed that both relays associated with "towing" or "trailer" are functioning correctly; not only do they click, but they have minimal resistance (0.2 Ohms) when powered.

Note that I do not have any trailer brake controller installed. (I know there's a factory-installed connector for it in the driver foot well; there's nothing connected there.)

I've heard there might be a towing relay behind the panel on the driver's side of the trunk. Should I pull that panel next?

What's the next troubleshooting step I should perform?

Thanks!

  • Welcome to Motor Vehicle Maintenance & Repair! – Pᴀᴜʟsᴛᴇʀ2 Sep 3 '18 at 20:40
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    I'm not sure you're going to get any power out of it without a brake controller installed. – Pᴀᴜʟsᴛᴇʀ2 Sep 3 '18 at 20:42
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    Most newer factory brake controllers are smart and will not put any voltage to the brake wire unless a trailer is connected that has trailer brakes. There has to be a brake controller before there is any voltage on the brake wire. – Moab Sep 3 '18 at 20:43
  • @Pᴀᴜʟsᴛᴇʀ2 Thanks. I’ll install a brake controller and re-test! – Steve Betten Sep 3 '18 at 21:04
  • @Moab Thanks! I’ll install a brake controller and re-test! – Steve Betten Sep 3 '18 at 21:05
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@Moab @Paulster2 The solution is to install a brake controller as indicated in the comments on my question. Thanks!

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