This was a project I undertook so I could control my car stereo using the controls of a Tiptronic steering wheel (I have a six speed transmission). I also used the project as an opportunity to upgrade to the 3-spoke steering wheel. Since my radio has a Sony external wired remote input I could control the radio using a Sony RM-X4S or RM-X2S wired remote. These wired remotes are just resistor networks that give a certain resistance for each radio function. To control my radio, I just needed to add a resistor to the Tiptronic buttons for each radio function I wanted. Currently the steering wheel controls volume up, volume down, next track, and previous track. Although this DIY applies to a Sony radio that accepts an external wired remote input, I believe it can be adapted to other radio applications. I offer some suggestions at the end of the DIY.
Porsche parts required:
Tiptronic Wiring Harness (optional): 000 043 203 10
Standard 3.5mm stereo plug
Resistors (various values) or other radio control adapter
M 24 hex socket
Screw drivers (various sizes)
20, 22, or 24 AWG wire (various colors)
Splices or soldering iron & solder
Shrink sleeve (optional)
993 factory wiring diagram (optional)
First disconnect the
battery. Remove the steering wheel, airbag, and plastic trim cover.
Undo the screws holding on the airbag using a Torx T30 socket drive. Disconnect
the airbag connector and remove the airbag (store the airbag with the padded
side facing up). Remove the nut from the steering wheel using a M 24 hex
socket. Turn wheel straight-ahead and mark position of steering wheel to
steering shaft. Lift off the steering wheel and the spring washer. Undo
steering wheel trim cover screws on the front and both sides of the unit.
Remove the screws from the steering wheel contact unit but do not remove
Take your Tiptronic steering
wheel and disassemble the Tiptronic steering wheel control buttons. First
remove the horn contact ring (not shown in photo) by unscrewing the
torx screws using a T25 bit. Next remove both button covers by unsnapping
them from the switch assemblies (be careful not to break the buttons).
With the button covers removed, remove the exposed screws on each side
of the wheel that hold the switches to the wheel. Now you can remove the
Tiptronic switches from the steering wheel.
Add resistors (for a Sony radio) to the switch assembly to control the radio functions. The Tiptronic switches are made up of two different switches wired together to control shifting of the automatic transmission. These two sets of switches allow for up to four radio controls. Using the table below, add the appropriate resistor or resistors after each switch for the functions you desire. Because of the way the buttons contact the switches, make sure that you add the right resistor where you want it. Review the Tiptronic transmission section of the 993 factory wiring diagram to see an illustration of the switch wiring. Basically one side of the "+" switches are wired together and then tied to one pin and one side of the "-" switches are wired together and then tied to another pin. The other side of all the switches are tied to ground. To modify the buttons, add the resistors, connect all the switches to the same pin, and connect the switch ground to the other unused pin (see diagram below). I soldered all the resistors and all the rewiring to ensure a good connection and to save space. However, you could also use splices and crimp connectors to make the modifications. Use electrical tape and/or shrink sleeve to insulate all the connections.
BR/YE= Brown/Yellow wire.
BR/RE= Brown/Red Wire, BK= Black wire
Front, middle, and back are special Sony radio functions.
Check the operation of
the switches using a voltmeter to ensure that each switch gives the correct
resistance. You don't need the exact value shown in the table but you need
to be in the ballpark. Reinstall the switch assembly back into the steering
wheel by reserving the previous steps.
Remove the steering wheel
contact unit that was left on in step 1. To remove the unit, take off the
two screws and unplug the connectors attached to the harness on the unit
under the dash. These connectors may be wire tied to another harness so
you may have to remove the wire tie before you can get the connectors separated.
Install the new support for contact (horn contact) reversing the previous
steps. Please note where each connector is located because they are not
keyed. You can identify the correct connector locations by the wire colors.
The new support for contact
(horn contact) has three connectors - one for the horn, the air bag, and
the tiptronic controls. Once the horn and air bag connectors are plugged
back in, the tiptronic control connector will be free. At this point, you
can plug in the optional Tiptronic Wiring Harness (000 043 203 10) to extend
the connector wires, make your own plug in connector, or cut away the connector
and splice right into the wires.
Next you need to make
your own 3.5mm stereo plug harness for the radio connection. Using some
20, 22, or 24 AWG wire, connect/solder one wire to the Tip ("right"): resistor
sense of the 3.5mm stereo plug. Connect/solder the other wire to the ring
("common"): ground of the 3.5mm stereo plug. The "tip" of the plug
is usually the "right" wire of the stereo plug and the "ring" is usually
the metal sleeve shield of the stereo plug. Insulate the connections with
Now connect/solder the
"tip" wire of your 3.5mm stereo plug harness to the wire or pin of the
support for contact harness that is tied to the resistors. Connect/solder
the "ring" of the 3.5mm stereo plug harness to the wire or pin of the support
for contact harness that is tied to ground. Check the operation of the
switches again using a voltmeter to ensure that each switch gives the correct
resistance when pressed. To check the resistance, connect one lead of the
voltmeter to the tip of the 3.5mm stereo plug, connect the other lead to
the "ring" of the 3.5mm stereo plug (the ring is the third metal section
furthest from the tip) and press each tiptronic button. You may have to
adjust the range of the voltmeter to read all the resistances.
Finally connect the 3.5mm
stereo plug into the radio, reinstall the plastic trim covers, airbag,
and steering wheel, and reconnect the battery. Make sure that you plug
the the connector from the steering wheel control into the connector from
the support for contact. Check the operation of the radio by testing all
Suggestions for other radios:
1. Pacific Accessory Corporation make a unit called the SWI-X. that is an integration device that turns your car's factory radio steering wheel controls into infrared commands compatible with aftermarket radios. You may be able to integrate the tiptronic controls into this device and program it for your car radio.
2. You could try to hard-wire your infrared aftermarket radio remote into the tiptronic controls and then mount your remote insight of the radio.
3. There are probably
some other creative solutions that I have not thought about.
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