mfg_guy

Ok, I believe I have attached photos of the seat wiring from the 98 electrical service manual. In addition I did some p/n searching and confirmed that manual SC300's have a different drivers side ECU from automatic SC300 and SC400. I did this research a couple of years ago when I did the swap but couldn't recall the details. The p/n for the driver's side ECU on manual cars is 89710-24050. For auto cars it is 89710-24020. The passenger side ECU p/n is 89710-24060 for all models. These part numbers apply to all cars from 92-2000. As you can see on the attached manual page 208, top of the page, there is a connection from the A/T indicator switch to the driver's side ECU pin 15A. I believe this is an inhibit connection that prevents the memory function from working when the transmission is not in park. (I.e. can't use the memory function while in gear). I didn't see this connection on the schematics you attached. Since i don't have a manual for a SC300 manual transmission car, I don't know how Toyota inhibits the memory function while driving in gear with that ECU. So, if the OP used a seat from an automatic car with the 89710-24020 ECU in a 97 car with manual transmission, the memory functions will not work correctly. And possibly other functions may not work properly. If it was an auto to auto swap, it should gave worked fine. In my case (97 manual seats to 98 auto car), I believe I only had problems with the memory functions, but it was a couple of years ago so I can't be sure. As I said in the earlier post, the two ECU's are plug compatible.

t2d2

iTrader: (8)

Ah, that makes sense, being a seat memory issue not a power controls one, and how that pertains to detection of being in gear. Can't say I ever would have thought of that!

gerrb

iTrader: (34)

That Driver Side Seat ECU Pin A15 (15A) is not only for cars with automatic transmissions.

Why ? Because it is used by all SC300 / SC400 for all years regardless if the car has an auto transmission or manual transmission. It is the Pin on the driver seat ECU that determines if the car is moving or not . If it is not moving then it will allow the driver to save memory settings .


You have posted the detailed diagram and I posted the overall diagram from a 1998 which refers to exactly the same schematics . You can go over every pin and wiring on both schematics to verify.

Let me post the 1996 Seat ECU diagram on top of the 92-94( my very first diagram on this thread) and the 97 and 98 diagrams which I previously posted so you can see for yourself that the PIN A15 (15A) is used by every Lexus SC manufactured in different years . There are now 4 Driver Seat ECU diagrams from 4 different years on this thread which basically illustrates the diagrams from 1992-2000 cars . The SCs have been grouped as 1992-1994 , 1995-1996 , 1997-2000. Every group basically has same external looks and functionalities / wiring diagrams except for some minor differences .

1996 Driver Seat ECU Diagram . Observe the Pin I have enclosed in orange .. and check the 92, 97 and 98 diagram I previously posted . They all have it. That is the pin you were referring.


Where does that pin go ? On the following diagram, it will show you where it goes to a car with A/T and M/T. So regardless if you have an A/T or M/T equipped car , the pin is used by both.


Let me use a more exploded schematic of the diagram which you posted to show clearly that PIN A15 Exists in and is Used by all Auto Transmission and Manual Transmission cars . Do you see the Pin A15 ? For Auto transmission cars it goes to the diagram with (A/T) ... for Manual transmission cars it goes to the diagram with (M/T) . I have enclosed them with an orange outline on the picture below .

At any rate this diagram simply proves that the A15(15A) pin is not only for cars with Auto Transmission as you probably thought. You probably would say , hey , why is the diagram not on my 1998 detailed diagrams ? The answer is.... there were no manual transmission equiped cars from 1998 to 2000. So you will only see such exploded diagram from the 1992 to 1997 cars.



I know you said the part numbers are different for the driver side seat ecu for Auto and Manual Transmission.

Unless I see any difference in functionality which I believe can be deduced from wiring diagrams , IMHO , different part numbers doesn't necessarily mean they function differently. Just because there are a lot of times Toyota used different part numbers for the same part of the same functionality. Aside from what I previously said , let me give you another example..... Check the MAF and TPS of the SC... you will find that along the production period , Toyota used different part numbers but it is exactly the same MAF or TPS you can interchange to use in different years and at times even different cars .

Don't get me wrong though , I am not saying that the driver seat ECU are exactly same for auto and manual transmissions. All what I am saying is I don't see any difference on functionalities so far by going through the car's electrical diagrams. Without seeing the diagrams inside those seat ECUs or seeing a description of functionality between the two , it will be hard to tell. At this point, I see more similarities in functionalities and yet to see a difference myself.


With the diagrams I have posted on this thread so far as proof , I will disagree on these statements about the Driver Seat ECU pin A15 . The diagrams from 1992-2000 either for A/T or M/T cars clearly show that they all have it on their wiring diagrams and they all use that A15 pin.

gerrb

iTrader: (34)

After doing a lot of reading and more extensive research on informations coming from the Toyota Information System whose site link I wrote in a previous post, I am now inclined to believe what mfg_guy previously said :

"IF YOU HAVE A MANUAL TRANSMISSION CAR , you will need to use the Driver Seat ECU from a manual transmission car. The auto transmission car driver seat ECU is different AND VICE VERSA. " .

BUT , if you know how to do some simple wiring , you still can ... there is a solution to this. You can trick those seat ECUs , pretending that your car was an originally auto trans equipped even if it had a manual trans and vice versa ... EASY !!!

Even if all SCs uses that pin 15 of the Driver Seat ECU as I have proven in the previous diagrams I have posted , after more investigations , analysis and testing with my SCs , both with auto and manual transmissions, that pin is used differently on the drivers seat ECUs between said cars. What it means is inside the auto / manual driver seat ecu , there are differences. They have same purpose though for that pin , which is "to check whether the car is in motion or not . Memory settings can only be done when that pin senses that car is not on drive ."

This may also explain the difference in part number for the Driver Seat ECU for auto and manual trans car. I will continue doing research to confirm such findings since I am not someone who just agree and regurgitate blindly what my mechanic or brother or uncle say . Got to find proof to be convinced .

Even without posting a lot of the other diagrams I came across on the TIS website , one would be able to tell this just from the diagrams I have posted so far if you know how to read diagrams and should be able to figure out how to trick those seat ECUs so you still can use one to the other.