Hi,
This is an update to an older thread that I used as a guide. The old guide is incomplete, there's a lot of speculation in the thread, and this is a known working solution that shouldn't be buried under BS. Older Thread

The old thread is for 98 GS300 that didn't have SW controls from the factory. The person bought one from an SC and then made it work. I am adding the wiring for a 01-05 GS. One major improvement is the use of a Maestro SW to convert the analog signal.

FIRST: Axxess claims to sell a product that fits these cars. Apparently it works on some cars, but not cars with Navigation and Mark Levinson audio (I tried and it does not). At one point I did talk to their jerks in tech and someone mentioned there was another product that would plug and play. I doubt this, but if I could start over I would have tried anyway. That info was too late for me, I had already butchered the controls. So if you order the Axxess be prepared to send it back or to call their tech people and ask for the actual part that SHOULD work.

NOW: So you've abandoned hopes of using a plug and play approach. You want to build an analog SW controls using the OEM Lexus unit.

Remove the controls from the wheel by pulling the back of the control cover away from the wheel. This will leave the circuit board still attached to the wheel. Two more screws removes it from the wheel, and then you unplug.






Now you need to further disassemble the circuit boards from their case to access the locations to solder. (See other thread for solder locations)

I choose a range of resistors from 1kOhm to 4 kOhm. The older thread uses a wider range. The wider ranger is technically better, but the Maestro worked w/ mine. NOTE: Two of the switches are connected through a resistor. So it's likely your exact resistance values will not match your choice exactly.

I also cut away some of the older board to make room for the wires like the older thread.

You should end up with a switch network with two wires. Measure and record the exact resistance of each of the switches.

My understanding of the Maestro SW is that it will work in a one-wire system. One wire goes to the Maestro one wire goes to ground. I used a two wire system because I was fighting with Axxess and they said two wire. So the following is how to use a two wire system, but there is a ground in the steering wheel clock spring and if used, you would just need to have one wire go to the Maestro.

On the car side of the clock spring, the plug for 01-05 GS430 is:
1: MPX1 Blue - White (This is for the steering wheel controls [possibly for tiptronic if you have a GS300]0
2: B+ Green - White (Body ECU1 sometimes called CPUB. This powers the OEM SW controls)
3: TSW Black - Orange (To telephone)
4: Ground Brown (Ground for steering wheel)
5: Cruse Red - Yellow (ECM looks for ground/resistance)
6: Horn Green - Black

I used both the TSW and the MPX1 for my two connections to the clock spring.
Go in and cut the wire(s) you are using, leaving about two inches of wire between the clock spring plug and the cut. Strip and splice a wire onto the clock spring side and run that wire to your Maestro SW.

The Maestro SW will need acc power and ground and will need to connect to your headunit.

To determine the wire(s) to use on the wheel, use a DMM to find continuity between the SW wires and the wire(s) near the clock spring. If you are going (one wire) to use the ground in the wheel, determine what wire shows continuity with a known good ground.



Connect up the SW controls to the wires in the wheel.

The Maestro uses a web based interface to program. You get a free account. Connect the Maestro box to a PC w/ USB. Navigate through their web interface to “Program a Car Not On the List.” This will have you input a bunch of car specific info that you can skip over or put in gibberish. You’ll input the number of sensor wires (one), and the number of switches (6). Then you input the measured resistance values. NOTE: You may be able to program functions if you press two buttons at the same time, as long as the measured resistance isn’t very similar to another button.

Next you assign the buttons to specific radio functions. You can assign different functions to buttons you hold down. (ie. I’m using long hold on “Mode” for Siri).

The unit is then programed. Hook up the Maestro to you car. When you press a button you should see the unit flash an LED the number of times according to the number of the button and it should control your radio.

Congratulations, you may now bask in the laziness of not reaching over to your stereo to change functions, or like me, have a workable “Mute” button.

 

I I love you!! This is something I really wanted to investigate, I have a new, aftermarket stereo and it’s setup for adaptable steering wheel control, but my car wasn’t equipped with S/W controls. I came across the component in a wrecking yard, but I have never done anything with it because I didn’t know where to start. This will be helpful, thank you very much