This guide will take you through retrofitting a 2008+ Lexus IS250/350 steering wheel into a MKIV Supra with a 94-97 style steering wheel. The paddle shifting and rolling antilag portions are specific to ProEFI users... but I think I'm the only one in Winnipeg with one
I'll break the FAQ into a few sections and throw in pictures/tables/etc. to help with understanding all the steps. This took me an entire day to map out, even with pointers so please enjoy to the fullest.What is needed:
2008+ Lexus IS250/350 steering wheel with paddles and buttons
2006+ Lexus IS250/350 airbag
Lexus IS300 airbag (we will only use the ignitor cartridge on the back)
PAC-SWI RC (Steering Wheel Audio Interface)
PLCC-2 white LEDs (I'll double check how many again) for button illumination (OEM:green)
Quality soldering iron: preferably with temperature control
Optional: Smoke absorbing puller fan (don't want lung cancer...)
63/37 rosin core solder
Mechanical helper hands (so awesome!)
Straight edge cutters
Needle tip tweezers
3 sizes of Phillips head screwdrivers
Small flathead screwdriver
1/4W Resistors: 180, 220, 270, 560,
Resistors from old 94 style steering wheel for straight swap *NOTE: 98 style wheels use the same resistors and so a swap wouldn't be necessary*
Bunch of 22ga wire, different colours help
Lots of 3/32" shrink tube
======================================OEM Steering Wheel Harness
-Snip it right off. Here's a table I made of all the pins, colors, functions, and the plan!
*Note: Yellow wire (Disp) will be used as the Rolling Antilag button!
It will splice away before the PAC-SWI to the ProEFI on an Analog pull-up resistor Input.
Here is a scan of the LH and RH audio controls. It doesn't show the Display button. I have mapped out all the resistors and overlaid them in red for your curiosity!
======================================Paddle Shifters for use with ProEFI
This is a basic diagram I made, showing, basically, how the shifters are wired up. Resistor R1 is optional, but I put it in there anyway. This method allows us to use a single input and each switch has a different resistance value that the ProEFI can read to differentiate the upshift VS downshift.
(I believe you just need to solder in red-red and black-black on 1998 style)
(1994 style steering wheels only)
There are 3 wires from the factory and you'll only be using two.
-Connect White/Black from the old stalk to White on the IS250 stalk.
-Connect your Red/Yellow and Light Blue wires together from the old stalk and then solder to Red on the IS250 stalk.
-Remove the three resistors found on the board.
-Apply flux to the pads
-Replace with the resistors from your 1994 style steering wheel cruise control.
The IS250/350 airbag is two-stage so it has 4 connectors. We will convert it to a single stage by swapping over the ignitor cartridge from an older Lexus IS300. It is an identical fit but it's single stage, so it only has 2 wires like our beloved Supra airbags.
I'll have more on this Thursday when I get my IS250 airbag in.