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Wiring error in THAR-ONE-TOY9 with SIENNA 3rd gen.

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A wiring error has been found in the low-current part of T-harness THAR-ONE-TOY9 (THAR-TY30 Rev. 1 LOT: 51096) when installing on Toyota Sienna LE 2019.

The remote starter in/out wires for the AUTOLIGHT from EVO-ONE, pins A17 (Green/White) and A18 (Green/Red) are connected to a wrong pin of the Body ECU white 30-pin plug: they are connected to pin #6 instead of pin #28. This results in tripping a signal from the right rear (sliding) door trigger instead of the AUTOLIGHT signal.

The problem applies to the installation of this T-harness on all 3rd gen. Siennas. The correct info on the Body ECU white 30 pin plug wiring can be found here: https://www.the12volt.com/installbay/printer_friendly_posts.asp?fid=3&tid=122207

To the contrast, the wiring diagram on the installation guide without this low-current T-harness is correct (Guide #72751), the AUTOLIGHT signal being taken from a different connector (on the steering column).
asked Oct 7, 2019 in Toyota by Alexey Kozlov (430 points)

1 Answer

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We dont interrupt the autolight in the t-harness install. That pin is meant for the driver door pin.
answered Oct 7, 2019 by Robert T (285,590 points)
the reason is because some toyotas do not have actual autolights
a request to have it checked is sent


Thank you!
The THAR-TOY30 is wired to shut down auto lights after remote start.  It is purposely not wired to pin 30 so that the harness can be used on various cars in which pin 30 is not an autolight wire.


Leaving the switch in AutoLights means you have decided to let the car decide how to control the lights.
(1) Pin #30 is Parking Light signal. It is coming from the headlight switch to the BCM. The T-harness is wired to that pin and there is no problem with that. This pin is not interrupted, it just tapped in. It is used by the remote starter to control the parking lights.

(2) The Auto Light signal on pin 28 is another signal also coming from the headlight switch to the BCM. This wire should be interrupted if you want the remote starter to control the Parking Light when the headlight switch is in Auto position. Otherwise applying a signal to pin 30 has no effect. According to the guide for the installation without T-harness, the Auto Light signal is interrupted by the remote starter using pins A17 and A18. This signal is taken from the steering column rather than from BCM connector pin #28 but it does not matter since it is the same signal.

(3) In the installation with the T-harness, the remote starter pins A17 and A18 are wired to interrupt the pin #6 which is a right rear (sliding) door trigger. It is very easy to demonstrate that. You need to disconnect EVO-ONE from the T-harness but keep the T-harness connected to the car. In this case, that signal will be permanently interrupted. When you open that sliding door you will see that there is no door open indication on the dashboard LCD. This is what I observed on my car. Interrupting a door trigger signal means you do not want the BCM to know that somebody has opened the door. Doing that totally makes no sense. Obviously, there is an error in T-harness.

(4) To fix the issue, I took a needle and a very small screwdriver and exchanged pins #6 and #28 on the T-harness. I did that on both male and female 30-pin connectors of the T-harness. After this modification, the remote starter wiring is equivalent to the installation diagram without T-harness. The right rear door trigger signal cannot be interrupted any more but the Auto Light signal can now be interrupted by the remote starter.
Thanks for the update. As mentionned, in the T-harness install we do not interrupt the Autolight in that connector since it's a different pin in every car that the toy30 is used on.


The reasoning, if you leave the switch in Auto, you're telling the car to manage the lights. Obviously this can be bypassed by interrupting the auto lights by that is the technicians choice.


i agree with point 3. It will be brought up to R&D.
Hi Rob,

I have found that A17 and A18 are permanently closed inside EVO-ALL, at least, with given firmware. The autolight singal is never interrupted by EVO-ONE. So, my modification of T-harness has no effect. EVO-ONE still cannot control the parking light wheh the headlight switch is in AUTO. But this solves the issue with intitally wrong wiring of this T-harness for Sienna: the right rear door trigger signal is also never interrupted. This raises another question: why do the no-T-harness guides (#72741 and #72751) require installers to cut the autolight wire and connect it to A17 and A18? This seems to be a useless job.

Finally, do you have any solution to fix the autolight interruption with Sienna?

Take the pink wire which is a (-) parking light output and use it to trigger a relay that would open the autolights wire.  I believe it's already being used so you would have cut it and split it with 2 diodes first.


A17 and A18 are not a relay. One side reads, the other outputs. orientation of the two wires are important.
Thank you for your answers. Currently, A17 (green-white) is connected to headlight switch and A18 (green-red) is connected to BCM. This is the way the T-harness was done initially (except swapping the right rear door trigger and auto-light signals). But this is opposite to the no-T-harness guides (#72741 and #72751). In those guides, A17 and A18 are swapped compared to my setup. In my setup, the headlight switch is always working fine which means the auto-light signal from the headlight switch always passes through EVO-ONE. So which wiring of A17 and A18 is correct: my current setup or the guides #72741 and #72751?
You can try with the Yellow/Red & Yellow/Green from the red connector. If that fails, wire your own relay to interupt autolights.