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Zeke21 09-13-11 04:24 PM

Key Remote ROM location
DIY - For the 1992 SC400 Stock/OEM Keyless Entry replacement (Keys and ROM Chip). 09/14/2011

The keys I got when I picked up my SC400 were pretty toast. It came with the original two masters and one sub key. One of the masters was totally missing the loop section to slide it onto a key ring and the other was about to also lose its loop as it was cracked. Only one of remote chips within one of the master keys worked, it happened to be the one with the broken loop and was also missing the button, so it sat in a zip lock bag. My sub key was nothing but metal practically as all the plastic was nearly gone and it too sat in a bag. Within a few weeks of having the car, my only key that still had the loop for placing on a key ring broke. It also was the one with the bad remote chip. I decided to purchase a new key as I wanted to be able to loop the keys onto a ring and I really like the stock keyless entry set up. Plus I just wanted a set of nice looking keys.

If your keys are still in good shape, ie. they'll still go onto a key ring, then you may want to check out O.L.T.'s thread about other options on repairing the remote system. You may just need to resolder the antenna inside the key. see:

After some research I found out Lexus offered master remote keys in a
1 key set
2 key set (Toyota part#89705-50944)
3 key set, which I was told has been discontinued.

These 1 or 2 keys sets also come with a ROM chip. The ROM chip is NOT programmable and only works with the chips found inside of the key set you purchase. This is why the earlier year SC's keyless entry cannot be reprogrammed. In other words to get your OEM keyless entry system working again if you don't have a master key or if the chip in your only master is toast or the keys themselves are in bad shape, (make sure you have the rest of the system checked out to ensure you don't have a different problem - see O.L.T.'s thread above) you have to get both - key(s) and the ROM together at the same time. The ROM is placed into the keyless remote ECU.

I figured if I was going to have to get a key and ROM I might as well get two master keys, so I purchased the 2 key set. I purchased mine from the dealership for $280.00, this also included their cutting fee. They wanted an additional $130+ for labor to install. For those of you looking to save $130 or more, this is for you!

Sorry, I only had my phones camera to shoot these photos.

The new keys and ROM chip.

1. The keyless remote ECU is located underneath the passenger rear quarter window. To get to it, you must remove the bottom of rear seat. Simply straddle the center hub in the back and place your hand towards the center of the two rear buckets in the set and pull upwards. The seat should lift out pretty easily. The red circle in the photo is the location where the seat hook snaps into.

2. Remove the plastic screw at the bottom of the interior trim as circled in the photo. Remove the plastic screws that hold in the seat belt track on the interior trim.

3. Slightly remove the trim piece running along the door frame so that the quarter panel trim piece can be lifted upward and away from the inside of the car. Gently pull down and away the trim piece from the car.

4. You should now be able to view the keyless remote ECU. Remove the two 10mm bolts and unplug the harness and antenna cable running to it.

5. Look for a small metal door with one screw on the ECU. Remove the screw and the door should pop open. This is the access slot for the ROM chip.

6. Gently use pliers to pull the old ROM out. You don't need to put a lot of pressure or squeeze the pliers hard. You only need them to grab and pull the ROM.

7. Putting the new ROM in will take some pressure from your hands. Try not to apply too much too fast but take your time pushing it into the slot. I worked with mine for a bit in fear of breaking the ROM. It will appear to move in half way and stop keep pushing and eventually you'll feel it snap in. Just take your time and use caution.

8. Once in, place the door back on and screw it shut. Plug the antenna cable and harness back into the ECU. Remount the ECU and begin putting back together the interior trim and seat.

9. Stand back and enjoy keyless entry and your very clean and new key(s)!

Note: With my original good chip and original ROM I guess I have an extra set of remote entry equipment. Does anyone know if the chips in the keys are removable. I opened my old ones up and it looks like they might be but I wasn't certain. Thinking I might be able to salvage the good parts out of the two masters.

Also if anyone else knows which other years for the SC require this same set up let me know so I can adjust my model year range on the DIY. I think 92-95 all use the same key chip and ROM package set up, i.e. not programmable.

*Hoping an admin can change my thread title to "DIY - For the 1992 SC400 Stock/OEM Keyless Entry replacement (Keys and ROM Chip)."

Starfx5 09-14-11 09:49 AM

mines was in the front end either behind the bumper or the fenders not to sure tho:uh:... srry if this dosent help:sad:

Zeke21 09-14-11 03:29 PM

Thank you for the help. I did find it and it was located behind the passenger seat and below the rear quarter window. I took some photos and will post a DIY soon! Got the keyless entry working again!

MMCtuner 09-14-11 06:50 PM

Nice!! How much and where did you buy it?

Zeke21 09-15-11 08:27 AM

Updated my original post with the DIY.

Asha'man 09-17-11 01:08 PM

Nice writeup. Does your keyless work like brand new now, with good range and all?

7akata 09-17-11 01:57 PM

Awesome DIY. And here I wondered why I bought my car with only one key that looks like a valet key... lol

Zeke21 09-24-11 09:17 AM


Originally Posted by Asha'man (Post 6687924)
Nice writeup. Does your keyless work like brand new now, with good range and all?

Range is good and it works perfect! I only wish the car flashed its turn signal lights or something...cause when you far away from the car you cant tell if it in fact locked or not.

7akata 09-24-11 12:13 PM

I just called my dealership today about this. My 1 key cost was 250 and the2 key was 390 something :/

Zeke21 09-24-11 12:22 PM


Originally Posted by 7akata (Post 6703396)
I just called my dealership today about this. My 1 key cost was 250 and the2 key was 390 something :/

Call a few different dealerships. First one I called wanted $475 for the same set. Cheapest I found was $280.00.

7akata 09-24-11 12:25 PM

Yeah, unfortunately I live in Oklahoma City, and there's only one Lexus dealership in the city. I guess I'll have to wait till I go out of town to check and see other places prices. Thanks for the DIY though.

Zeke21 09-24-11 12:44 PM

You might try calling the next few closest to you and see if they will ship it to you only concern is how you could prove ownership. My dealership wanted to see the registration and my driver's license before ordering.

7akata 09-24-11 01:13 PM

Yeah I will call and check around. I asked the dealer here, whom I called, and he said all they need is my VIN number, and they have Lexus cut them and send them everything, and they in-turn give it to me.

danegerous 10-15-11 05:04 PM

Amazing. So what's the deal if mines is a 95? Replacement keys are programmable?

BenStoked 10-15-11 05:37 PM

Very nice writeup, will have to do this sooner or later.
anywho, for those wondering about part numbers,
1 key and chip 89705-50943
2 keys 89705-50944
3 keys 89705-50945

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