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I have attempted this install today. However, I don't know if it is possible to complete this project. It looks like I am missing the Heated Steering Wheel Relay Wiring from Engine Room Sub Relay Box.
Here is what mine looks like:
HERE ARE PICTURES OF THE STEPS I DID NEW STEERING WHEEL, CLOCKSPRING, AND BUTTON REMOVE OLD STEERING WHEEL AND CLOCKSPRING ADDED THE BUTTON, THE PRE-WIRING WAS THERE FOR THE BUTTON WIRE CONNECTED EVERYTHING INSTALLED. FINGERS CROSSED DIDNT WORK SO I CHECKED THE FUSES. THE ONE FOR THE HEATED STEERING WHEEL WAS MISSING SO I PLACED ONE THERE. STILL DIDNT WORK.
IN THE END I FOUND THE RELAY BOX AT THE BEGINNING OF THE POST. I THOUGHT I COULD JUST BUY A RELAY FOR 5 DOLLARS BUT IT LOOKS LIKE THE WIRING IS MISSING.
SO, DO I NOT HAVE THE RIGHT ENGINE ROOM WIRING HARNESS TO ALLOW A HEATED STEERING WHEEL??? PRETTY SAD IF THAT IS THE CASE GIVEN THAT I WAS ABLE TO DO THE RADAR CRUISE RETROFIT WITHOUT A NEW WIRING HARNESS.
Sorry to hear it after the work you have put into it. Any chance you can run some custom wire runs?
This may be another one of the mods where wiring harness doesn't support the project. The harnesses that need to be there for mirror cameras aren't present in my '12. In addition, the wiring connector for the auto high beam rear view mirror is different but that may just require a few extra wires to run to BCM.
While the '10-'13 have it...the '14+ do not have the pre-installed wiring up front for camera and radar sensor either.
If it is simple to do then I would consider it. I’m not even sure where to start on the attempt.
It appears I am missing 4 wires that goes into the relay sub box. Not even sure why there is a sub box? Lack of room in the main fuse box? Not sure why the sub box has wiring for rear seat heaters but not wiring for the heated steering wheel. All very strange.
@clearmysix I’ll need to check that sub box tomorrow and report back what’s in mine. I noticed yours didn’t have headlamp washers or a wood steering wheel from the factory. It’s odd to have the pre wiring for the button and for your radar cruise, and for them to skip the relay.
theres an ecu, at least on the version i looked at. this will control the auto off timer, the default heat setting and the thermistor feedback temp control
easiest might be to connect to that ecu
another option is to either connect your own wiring and switch and use the thermistor or some other circuitry to control the heat.
should be able to use a <15$ controller with an el cheapo 5$relay. if you dont want relay clicks when it goes on and off then use a dc-dc ss relay ~10$
might need either a different switch, a latch circuit, a timer relay or another method to keep the controller powered
i would go with 15A or more for the final power to the heater
thermistor is 10kohms, heater is 2ohms
should be able to cut off the included thermistor and attach to the connector for the wheel.
the controller is 120W, while the wheel will go above that, so use that to control a larger relay.
i believe the switch you have is momentary while this controller needs continuous, so the options above can be used.
its doubtful that lexus has 2 versions of the ecu so most likely you only need to connect what you have. if for some reason the stuff you already have dont work then what i posted should work no problem.
as always, bench test before putting onto the gx
in the diagram above you can see lexus uses their ecu to control a larger relay to supply the 12v
After reviewing the electrical circuits for the heated I am convinced that I am simply missing one wire to get this job complete. I would like to do it as OEM as possible, so I am thinking of tapping into the unused rear seat heater relay to power the circuit.
Here is the only wire path that I think I am missing. What do you think about this?
if all youre missing is the power to the heat element, then your idea should work. tapping depends on how and what you tap.
first thing to know is that seat heaters use a 20a fuse while the steering uses a 10. if you want to tap (meaning tee into or run parallel) to the seat circuit i recommend to change that fuse to a 10a. if you do this, and turn on two of the 3 heaters simultaneously, you will blow the fuse. if you just use wheel heat you are ok and maintain oem current protect values for the wheel. if you do this you might want to disable/disconnect the seat heaters. this would work but not how i would proceed.
if you leave the 20a in there you can get a scenario where the wheel had a problem and pulls 15a while oem protection was at 10a. recommendation is dont do this method. you could end up with major damage.
if it was me i would add a 10a fuse and a relay, then you are basically going to oem protection without impacting the seat heater circuit. this is the recommended method. you dont need to use the oem relay socket or location but you can. its only a few wires and <25$. well worth it to be safe and not lose ability to use other features at certain times.
No updates unfortunately. I'm not smart enough to understand these wiring diagrams to figure out a solution to the missing relay. I only want to do this project if I can do it stock-ish. I don't want different switches. I am willing to try and use the rear seat heater relay for power since that is pre-wired and I don't have rear seat heaters, but since I don't fully understand the wiring it's going to be hard to figure it out.
Still basking in the glory of completing the pre collision / radar cruise project.
You have pretty much everything that is needed (assuming you haven't bought cameras)
Originally Posted by clearmysix
No updates unfortunately. I'm not smart enough to understand these wiring diagrams to figure out a solution to the missing relay. I only want to do this project if I can do it stock-ish. I don't want different switches. I am willing to try and use the rear seat heater relay for power since that is pre-wired and I don't have rear seat heaters, but since I don't fully understand the wiring it's going to be hard to figure it out.
Still basking in the glory of completing the pre collision / radar cruise project.
No updates unfortunately. I'm not smart enough to understand these wiring diagrams to figure out a solution to the missing relay. I only want to do this project if I can do it stock-ish. I don't want different switches. I am willing to try and use the rear seat heater relay for power since that is pre-wired and I don't have rear seat heaters, but since I don't fully understand the wiring it's going to be hard to figure it out.
Still basking in the glory of completing the pre collision / radar cruise project.
would it be possible to consult an audio/video vehicle store? Might be worth an hour labor to a tech that can read and figure out a remedy. I hate to see you come this far. Good luck.
10-13-19, 03:05 PM
