Best of Deals Car Reviews Repair Shops Cars A-Z Radio Show

Brake lights not working on Toyota Sienna 2005 XLE after emissions testing connected to the dataport

So I’ve got the exact same issue as the person who posted this:

Went to the Toyota dealership this afternoon and it looks like a wiring issue. Also found out when the left blinker is engaged, it blows the 10A STOP fuse which then causes the ABS and VCS(?) lights to illuminate. What a mess…

Is the easiest way to fix this just to run a new wire to the affected area? The folks at the dealership seemed to suggest they were going to need to rip out all the interior to find the break in the circuit.

Timing-wise, this problem starting happening right after I went to get emissions checked and they plugged a cable into the data port to pull emissions(?) and other data. My hunch is that these two events are directly related but I don’t have much knowledge of how things are wired up and hoping someone can provide some insight into what might have caused this problem.

They are not related. Under the rear of your vehicle is a connector that ties the left and right brake and tail lights together. If you have a trailer hitch installed, the connector is separated and a trailer adapter is plugged in between this connector. The fact that the fuse blows when you turn on the turn signal tells me that you have a trailer hitch and one of the wires in the trailer hitch adapter harness has shorted out against the body or the hitch assembly. I also suspect that that one side of the adapter has become disconnected.

The only way that this could be related to the emissions testing would be if for some reason, say a safety inspection or something, the vehicle was jacked up at the rear or it was put on a lift and someone accidently snagged the trailer wiring harness.

I have same issue no trailer hitch tho any suggestions

Lazydog, have you checked the uses?
Also try removing the bulbs one at a time, including the front bulbs, and see if one of them being removed stops the fuse from blowing. That would isolate the circuit that’s shorting to ground.

Shorts to ground usually happen by either erosion (chafing) or cracking on the insulation where the relevant wiring harness traverses the openings in the “bulkheads” that separate the harness from the body. If your taillights are on your truck or hatch lid and raise with said access piece, the constant flexing of the harness over the years as you open & close the hatch/trunk makes those key suspects.

So, you have two choices:

  1. try to isolate the circuit as much as possible, access, untie, and flex the harnesses with a good worklight searching for the insulation break, or
  2. find a good automotive electrics shop in your area.

If you can talk the dealer’s parts guy into printing a wiring schematic and wiring diagram (different documents) for the wiring, you’ll be able to further focus your efforts by using the color coding on the wires.

Post with how you’re making out. We do care.