Steering Wheel Radio/Stereo Control for After-market HU

[yojabbajabba]

Hi all,

After doing a fair bit of research, it seems that both the Axxess Metra ASWC and PAC SWI have NO information for how to wire up their respective Steering Wheel Control adapters. I am driving a 2008 Toyota Yaris YRS LB, but the closest thing I got to was this from PAC:
here

I am sure others have successfully installed one of these patch controllers - where do I go finding out where the wires all go (for both the METRA and PAC kits)?

Thanks :)

[Iggy888]

Hello yojabbajabba. I have done this install and can offer some assistance.

First of all, I would recommend going with the Axxess Metra ASWC.
The ASWC install requires fewer steps but more importantly it seems to respond faster than the PAC SWI when you press a button on the steering wheel.

If your car came from the factory with steering wheel audio controls:

The spot that you would connect the steering wheel control interface to your Toyota Yaris is Connector D74 (Radio Receiver Assembly).
Connector D74 is one of three Radio Receiver Assembly wiring harnesses that can be located once your remove your stock head unit.
D74 may be plugged into the back of your stock head unit or it may be unplugged and found near the other two Radio Receiver Assembly wiring harnesses (D10 and D11, which would be connected to the back of your head unit).

To add either the Axxess Metra ASWC or PAC SWI you tap into the following three wires from connector D74:
Pin 6: SWG (ground)
Pin 7: SW1 (Steering1)
Pin 8: SW2 (Steering2)

Those three wires from Connector D74 connect back to to the Steering Wheel buttons via the Spiral Cable assembly connector D3 (located under the steering column):

Connector D3:
Pin 4: EAU (common/ground for steering wheel control)
Pin 5: AU2 (mode switch circuit)
Pin 6 AU1 (volume +/-, Seek +/- circuits)

The image below shows the two connectors:
Connectors.jpg

The diagram below shows how this circuit is wired together:
Wiring Diagram.jpg

If you are installing the Axxess Metra ASWC, you would wire it as follows:

1. Connect the Black wire of the ASWC to ground.
2. Connect the Red wire of the ASWC to a 12 volt accessory wire, one that turns on and off with the ignition key.
3. Connect the Green/Orange wire of the ASWC to Pin 7: SW1 (Steering1) on Connector D74 [which leads to Pin 6 (AU1) on Connector D3]
4. Connect the Black/Green wire of the ASWC to Pin 8: SW2 (Steering2) on Connector D74 [which leads to Pin 5 (AU2) on Connector D3]
5. Connect Pin 6: SWG (ground) on Connector D74 to ground
6. All other wires on the ASWC would be taped up (to avoid short circuits) as they are not used.


The reason I mentioned Connector D3 and included a diagram of the whole circuit is for those who wish to add steering wheel controls to a Yaris which did not come from the factory with Steering wheel controls.

Since mine did not come with the factory with Steering wheel controls, it was not pre-wired to support them at connector D74.
I was able to add the steering wheel controls by purchasing the missing pieces:

-Steering Wheel Switches - Toyota Name: Switch Assy. Toyota Part #: 84250-52010-C0
-Spiral Cable assembly - Toyota Name: Cable Sub-Assy. Toyota Part #: 84306-52090 (#09) G-BOOK
-New Airbag with smaller airbag cover that supports Steering Wheel Switches
-an old CD ROM cable from a computer. (Cable consisting of three twisted wires which was used to provide analog sound signal from the CD ROM drive to a sound card)

Once installed, I wired the Axxess Metra ASWC directly into Connector D3 (located below the steering column) since there was no wiring in my car that connected D74 back to D3.
The old CD ROM cable was used because it already had the small molex connectors crimped on to its three wires and could be easily inserted into connector D4 at one end.
The other end of the old CD ROM cable was cut off and connected to the Axxess Metra ASWC as detailed above.

I hope this information helps you. Please feel free to post back with any questions. Good luck with your installation

[yojabbajabba]

Hi Iggy888 - Thank you so very much for your help! I shall now be able to do this project with a lot more confidence!

I have another idea - do you think it'd be possible to attach a second set of controls on my steering wheel (on the oppposite side to where they are now) to control the bluetooth Push-to-talk functions of my new head-unit? I see that you have listed parts above, are they compatible with both sides? and will this affect the airbag mechanism?

Thanks again!
Aaron

[Iggy888]

Originally Posted by yojabbajabba

Do you think it'd be possible to attach a second set of controls on my steering wheel (on the oppposite side to where they are now) to control the bluetooth Push-to-talk functions of my new head-unit?

Yes, that is what I have done.
The part number I listed earlier is switch controls for both sides of the steering wheel:
Toyota Name: 84250A STEERING PAD SWITCH ASSY.
Toyota Part #: 84250-52010-C0

Note: The last two digits of the part number indicate the colour:
B0 = Silver
C0 = Black

Left side controls = Volume Up/Down, Mode and Seek Up/Down
Ride side controls = Push to Talk, Answer Phone, Hang Up phone

The diagram below shows how both controls are wired together and connect together into one plug that attaches to the top of the spiral cable assembly (clock spring):
ImageFromDB.php.jpeg

Originally Posted by yojabbajabba

I see that you have listed parts above, are they compatible with both sides? and will this affect the airbag mechanism?

The switches will work provided the steering pad cover (air bag) has room for the switches on either side.

If you currently have a narrow steering pad cover (air bag) like the one pictured below then you can add the switches:
Narrow Steering Pad Cover.jpg

However, if your steering pad cover (air bag) is wider like the one below then there is no room for the switches:
Wide Steering Pad Cover.jpg


My car had the wide air bag cover so I had to replace the whole air bag too

Though people sell the narrow steering pad covers on eBay, the steering pad cover is riveted to the air bag.
Drilling into an explosive airbag charge to swap covers did not seem like a good idea

[yojabbajabba]

First of all, thanks for the reply!

Originally Posted by Iggy888

Yes, that is what I have done.
The part number I listed earlier is switch controls for both sides of the steering wheel:
Toyota Name: 84250A STEERING PAD SWITCH ASSY.
Toyota Part #: 84250-52010-C0

Note: The last two digits of the part number indicate the colour:
B0 = Silver
C0 = Black

Left side controls = Volume Up/Down, Mode and Seek Up/Down
Ride side controls = Push to Talk, Answer Phone, Hang Up phone

- Is there a part that only has the PTT/Answer/Hang Up assembly? I already have the smaller steering cover + vol. controls, and by a quick google search, I have found that the part costs approx. $130 USD? Is that reasonable? (And, where do you source your parts? Local Dealership? Online vendors?)

Also,

Originally Posted by Iggy888

The diagram below shows how both controls are wired together and connect together into one plug that attaches to the top of the spiral cable assembly (clock spring):
Attachment 45020

The switches will work provided the steering pad cover (air bag) has room for the switches on either side.

If you currently have a narrow steering pad cover (air bag) like the one pictured below then you can add the switches:
Attachment 45022

However, if your steering pad cover (air bag) is wider like the one below then there is no room for the switches:
Attachment 45024

- Since I already have my vol. controls on the wheel, does that mean the spiral cable is there already for me to plug in the bluetooth control assembly?

Finally, can you please inform me on what wires go from the ASWC to the Bluetooth functions also?

And thank you for the tip re: NOT drilling the steering wheel. Duly noted. :)

[Iggy888]

Originally Posted by yojabbajabba

Is there a part that only has the PTT/Answer/Hang Up assembly?

I am not sure. I think it only comes as the two switches together.
Try sending a PM to CTScott. He is another forum member here on Yarisworld and is a terrific resource. He may be able to provide a definitive answer.

Originally Posted by yojabbajabba

I have found that the part costs approx. $130 USD? Is that reasonable? (And, where do you source your parts? Local Dealership? Online vendors?)

I think $130 USD would be an average price for this part.
When I was first looking to do this modification I priced the part for approximately $120 USD from japanparts.com but I am not sure if that price includes shipping.

I purchased the necessary pieces second hand from echo_hrs, another forum member when he was parting out his Yaris.

Originally Posted by yojabbajabba

Since I already have my vol. controls on the wheel, does that mean the spiral cable is there already for me to plug in the bluetooth control assembly?

Yes, if you have working volume controls then you have the necesseary wiring and spiral cable needed to support the bluetooth controls.

Originally Posted by yojabbajabba

Finally, can you please inform me on what wires go from the ASWC to the Bluetooth functions also?

Good news here. Since the switches for the bluetooth controls are wired into the same circuit as the volume controls, just follow the wiring instructions I provided earlier and they will work too.

[yojabbajabba]

Thank you very much Iggy!

I'll save my pennies and keep trawling the "For Sale" section of the forum to get myself one of these switch assemblies. Thank you kindly!

[Iggy888]

You're welcome.
I am not sure if many people have the steering wheel switches for sale but with a little patience and persistence you may luck out.

[yojabbajabba]

Back again Iggy!

I have received my ASWC, and the harnesses necessary for my new head unit (which I'm picking up on Wednesday - Alpine CDE 133 BT). This is a good things, as it means I can now proceed to doing all preparation wring :D

So, here are my troubleshooting questions.

Connecting the ASWC harness to D74:
Quote:
"5. Connect Pin 6: SWG (ground) on Connector D74 to ground"

Does that mean I have to cut off Pin 6 and re-wire it to the Ground used in "1."?

Connecting the ASWC harness to D74 (general)
- When "tapping" wires, does this literally mean joining the wires from the ASWC in-line with the wires on D74 - i.e. stripping off a part of the insulation on the respective wires, and then soldering the ASWC wires in-line? I'd like to avoid cutting off the OEM harness connector.

That's about it for now,

Thank you for your help!
Aaron

[Iggy888]

Hello Aaron. It is good to hear from you again. I am glad you are making some headway getting your steering wheel switches ready for your new head unit.

Originally Posted by yojabbajabba

Does that mean I have to cut off Pin 6 and re-wire it to the Ground used in "1."?

Yes, the wire from Pin 6 needs to be grounded. I wired mine to connect to the ground used in step 1 and had no issues.

Originally Posted by yojabbajabba

When "tapping" wires, does this literally mean joining the wires from the ASWC in-line with the wires on D74 - i.e. stripping off a part of the insulation on the respective wires, and then soldering the ASWC wires in-line? I'd like to avoid cutting off the OEM harness connector.

Yes, cutting into the wires and soldering them together is the most secure way to join the wires. It ensures the best mechanical connection and best electrical connection.
Soldering the wires together is what the instructions recommend.

However, having said that I chose not to cut up my wiring harness. Instead, I used wire tap splice connectors since they could be easily removed later without killing the harness.
One big caveat with using tap connectors is to make sure to get the right size (I used 22-18Awg connectors).

Background: I had used tap connectors to install another component in an earlier project and had trouble getting it working. Looking closely at my new connections, they seemed to be held securely in place by the tap connectors. What I did not realize at the time was that though the wires appeared to be joined together with the tap connector, they had not made a good electrical connection.

It was only after I removed the tap connector and inspected the two wires closely that I realized the tap connector had failed to pierce the outer casing of one of my wires and contact the core wire for a good electrical signal.

Ever since that frustrating experience, whenever I use tap connectors I make sure to get the right size so that when clipped together it makes good electrical contact.
To be sure, I pull out my digital multimeter, set it for continuity mode, connect the leads to the ends of the newly tapped wires and listen for the tone which indicates a good electrical connection.

Below is a picture of what these tap connectors look like:
65-1280.jpg

I hope this helps!

[yojabbajabba]

Thanks very much for that Iggy - I have sourced some tap-connectors from a local electricians warehouse, and I have some photos to show of my handiwork on the harness with the ASWC, so thanks for your help so far!

ASWC in-line with Toyota-ISO.jpg
I hard-wired the ground and ignition from the ASWC to the harness
Alpine-ISO-Toyota+ASWC.jpg
And this is the harness 90% complete - just need to pick up those tap connectors and think about how I'm going to ground the D74 SWG without completely disconnecting it from the harness plug. I think I will be using tap connectors for that!

Thanks!
Aaron

[Stevet]

Hi installed android unit but can only get steering wheel switch “mode” to be detected (used to control anything) any suggestions

[kevinj93]

I had the same problem with an Android head unit.
Turned out to be the adaptor cable from the Yaris wiring to the head unit was not wired correctly.

If it's like mine, there is an adaptor cable from the head unit to the Yaris wires. See the diagram above for the pinout of the Yaris plug. The instructions for the head unit I have only shows the position of the wires on the head unit plug. The wire colours on mine after correction were black for ground on pin 6 , brown for sw2 on pin 7 and blue for sw1 on pin 8.