Retrofit RCF/GSF front seats on IS250 (2IS - IS MK2)

[ahmed24]

The front drivers seat on my 2006 IS250 which i've now owned since 2007 is quite worn and i've been considering swapping out for another second hand one. But given the age of the 2IS, the condition of all the second hand ones are far worse than mine (rather keep mine). Got me thinking about retrofitting RCF/GSF front seats as I really like the look of them. But they are extremely rare to find second-hand. And once or twice I came across them they were selling for 3k plus just for front seats. So that was out of the question.

I then considered, that a 3IS set of second-hand front seats will probably be in better condition than some of the 2IS ones for sale because of the 3IS being younger car. But I wasn't willing to spend much for second hand seats that didn't make much difference (I would rather get mine re-done). Then, I came across the following pictured RCF breaking and I thought to myself, let me try asking about front seats.....

I was quite sure either the'll have blown the airbags or if they are available they would want a fortune for the seats. I was really shocked when I was sent the following photo of the seat in the car and the reply just said £500 (nothing else, just a picture and £500)

I thought to myself, is that for 1 or for both. It was actually for both and was collection price. But as I asked if they could do anything better on the price, i was offered free express pallet delivery. So it was an absolute no-brainer for me. I instantly purchased it. Not knowing if I am going to be able to retrofit it or not, I thought it's worth the gamble because even if I didn't want the seats, I could sell them off for much more than I paid. And if I manage to make them work on the 2IS platform then technically it will become a plug & play seat for the 2IS and ISF platform which I could easily sell on later for a profit.

So here is the seats delivered:

Now, onto the retrofitting... The RCF/GSF seats have the same cooling fan system as the 3IS and 2IS. Except there is ducted air conditioned air that goes to the fan under the seat which then makes the fan blow air-conditioned air through the seat. I've addressed this with the following 3D printed simple solution:

Next... Does the rails on the seats fit the 2IS? Answer is Yes. They are the same as the 3IS and 2IS and all line up and therefore no need to make any adjustments to the rails.

The main 17-pin connector on the seat itself (Part number 90980-12373) is identical and exactly the same as the 3IS and 2IS and I suspect Lexus and Toyota use this same connector across most of the seats and models. The only thing is that the wiring and pins are different on the connector. 

After spending hours and hours studying the schematics of both platforms and comparing and tracing wires and testing them. I finally drew up a plan to re-pin the main connector and I had accounted for every pin from the original car. With the exception of the memory seat pin (which uses a single 1pin for MPX1 communication). I'll cover the memory seats later. Here's a picture below of the depinning:

The airbag connector is different but this I solved easily by transferring the loom over. As pictured below:

The seatbelt buckle is different and the 2IS seatbelt does not buckle into it. So, I transferred the buckle over from the 2IS to the RCF seat. The buckle on the RCF seat sticks up quite a bit as it's quite slim and low on the bottom corners. The RCF buckle has a nice sleeve for the buckle so it doesn't look bad when it sticks out. When I installed the 2IS buckle, I noticed the metal plate was visible and looked ugly. So I decided to transfer the buckle sleeve over too. The buckle work pictured below:

I have successfully installed the drivers seat. It's working very well. I have yet to do the passenger seat and will be doing this over the next few days as the wiring is slightly different on that side. I can confirm the following all work:

• Heated & Cooled working
• Buckle and seatbelt system working
• Airbag system working
• Power seat working

The only thing I have yet to finish is the memory profiles for the seat. Unfortunately the RCF/GSF seats use a new type of CAN body communication with dual wire which communicates the memory button presses with two wires from the door card. Whereas, the 2IS uses a single 1 wire MPX communication. There is two ways to solve the memory seat issue. Easiest is to just transfer the position control ecu switch on the seat itself from the 2IS seat over to the RCF seat. or the other option is to create a virtual signal converter. I haven't decided which method I will use for that yet. But as memory seats isn't something I use at all, I decided to install it without that function for now and I will address the memory seat later.

Below are a few pics of my drivers seat now installed. They need a good deep clean and conditon. Once i've installed the other side, I will post more pics and videos showing the seats working. So stay tuned. Updates on here might be a bit slow as I tend to prioritise updates and stuff on my instagram, so feel free to follow me on my instagram for more updates (link in my signature)

 

[Mr Vlad]

By the time you've finished with upgrading your car Ahmed it'll be by far the Best is250 anywhere 👌👍👏

[ahmed24]

2 hours ago, Mr Vlad said:

By the time you've finished with upgrading your car Ahmed it'll be by far the Best is250 anywhere 👌👍👏

Thank you 🙏 

[TadasC]

Great work as always Ahmed. But is it just a picture angle or seats look very tight fit inside 250?

[ahmed24]

11 minutes ago, TadasC said:

Great work as always Ahmed. But is it just a picture angle or seats look very tight fit inside 250?

Thanks 🙂 

The bottom cushion part of the seat is a bit wider but fits just fine. You still have space to access the door card pockets with door closed. It's super comfy but the seat does seem to sit a bit lower down so needs a bit of getting used to. The only part that becomes quite tight is the bit where the seat belt strap is on the seat. The RCF seatbelts I believe being a 2 door comes from the rear and goes through this strap. The strap adds a bit of thickness and depending on how you position the seat, the strap can start to rub on the B pillar. For example if the seat is adjusted to the max height and you bring the back tilted forward then it can start to rub. But for most people the seat is back enough that it wont cause an issue. I am considering removing that strap if it becomes a nuisance 🙂 

Suprisingly, even though the seats are bigger, the rear leg room and space seems to appear a lot more roomy now compared to my originals. I think the back bit they've slimmed down on the seat to create room at the back on the RC.

[TadasC]

5 hours ago, ahmed24 said:

Thanks 🙂 

The bottom cushion part of the seat is a bit wider but fits just fine. You still have space to access the door card pockets with door closed. It's super comfy but the seat does seem to sit a bit lower down so needs a bit of getting used to. The only part that becomes quite tight is the bit where the seat belt strap is on the seat. The RCF seatbelts I believe being a 2 door comes from the rear and goes through this strap. The strap adds a bit of thickness and depending on how you position the seat, the strap can start to rub on the B pillar. For example if the seat is adjusted to the max height and you bring the back tilted forward then it can start to rub. But for most people the seat is back enough that it wont cause an issue. I am considering removing that strap if it becomes a nuisance 🙂 

Suprisingly, even though the seats are bigger, the rear leg room and space seems to appear a lot more roomy now compared to my originals. I think the back bit they've slimmed down on the seat to create room at the back on the RC.

Thanks for the answer Ahmed, again great work.

[BkS]

Oh my, Ahmed! Now that I know RCF/GSF seats fit on the 2IS, I'll be on the hunt because I LOOOVE the design of the newer F seats. Can you share the schematics for the plugs? What changes did you make when you repinned it? 

[ahmed24]

On 9/18/2023 at 6:03 PM, BkS said:

Oh my, Ahmed! Now that I know RCF/GSF seats fit on the 2IS, I'll be on the hunt because I LOOOVE the design of the newer F seats. Can you share the schematics for the plugs? What changes did you make when you repinned it? 

When you find a set and ready to do it, get in touch and i'll assist you with the rewiring. The main connector needs re-pinning to match the harness of the 2IS. The airbag connector or harness needs transferring over. The seatbelt buckle needs to be switched over. Cooling seats work perfectly just by re-pinning, but for heated seats to work, the wiring needs  a bit of modification to transfer the seat heater controller module over from the 2IS to the RCF seat. I've done it in a way that the 2IS heater module is directly plug and play on the RCF seat. Below are two pics. First one showing the original RCF seat heater module. and the second one showing the 2IS seat heater module transferred over to the RCF seat.

 

 

And finally, i'm still finalising the memory seat bit and hoping to possibly get that working very soon too. But in the meantime everything works perfectly except the memory positions.

[Alvarofrfr]

Hey boss this was a super informative write up! Would you be willing to help me out with the color matching or repinning for the seats? I just picked up the red RCF’s and I can’t get them to move 😞 thanks in advance 🙏🏼
 

- Alvaro / 08 ISF

[ahmed24]

11 hours ago, Alvarofrfr said:

Hey boss this was a super informative write up! Would you be willing to help me out with the color matching or repinning for the seats? I just picked up the red RCF’s and I can’t get them to move 😞 thanks in advance 🙏🏼
 

- Alvaro / 08 ISF

Nice 🙂 Where are you based? LHD and RHD wiring varies. Unfortunately to get it all working, it's not as simple as just re-pinning the connector. I spent hours upon hours studying and reverse engineering some of the stuff on these seats to get this to work. Re-pinning only gets the following things working:

• electronically adjustable seats (full adjustment control)
• seat cooling

Then you have the other stuff that requires extra work like:

• Airbag
• Seatbelt buckle
• Heated Seats
• Seat Memory Position - This I am still finalising and almost got working, just have not had much time to work on my own car lately. Been too busy with customer cars

If you've got an ISF then I take it your original seat does not have seat cooling anyway. and the RCF/GSF seats have cooling. This can probably easily be added in by replacing the switch on the centre console anyway.

[ahmed24]

Interior still unfinished and work in progress. But finally got round to installing the Passenger side RCF seat too. Was supposed to do this ages ago but got very busy and the wiring for the passenger side seat is a lot different to the Driver seat and hence wasn't as straight-forward. Passenger seat has the occupancy detection system which involves a lot more work.

Full details on this and many of my other mods on my Instagram page.

Here are few photos of the passenger seat now in.

[JDM-Fiend]

On 1/8/2024 at 11:08 AM, ahmed24 said:

Interior still unfinished and work in progress. But finally got round to installing the Passenger side RCF seat too. Was supposed to do this ages ago but got very busy and the wiring for the passenger side seat is a lot different to the Driver seat and hence wasn't as straight-forward. Passenger seat has the occupancy detection system which involves a lot more work.

Full details on this and many of my other mods on my Instagram page.

Here are few photos of the passenger seat now in.

Looks fantastic, great job!