1993 SC400 lock and anti-theft Engine won't Start
 

Hello guys.
When i left my 1993 LEXUS SC400 i closed the doors with the Key Remote but after i came to my car then the Remote didnt work! So i opened the driver's side door with the master key. Then the Alarm started and i tried to open the driver side door by key but anytime i turn the key to the unlock but the door locks it by him self! Maybe security!? So i have to hold the key to the unlock side and then i can open the door! I Went around to the passenger door and had trouble unlocking on that side as well and the Alarm doesnt get off!
I jumped in the car and put the key in the ignition, turned it and the alarm went off but the car won't start. The car thinks I'm trying to steal it!! The trunk won't open, the manual lock buttons won't operate and I can't start the car.
My locks work by using key! I can lock and unlock the doors but only if the Alarm is on then i cant turn the key to unlock! It turns to lock by him self! I think its just the security!
im from Germany and my SC400 is very rare and Lexus Germany cant help me :-(
My only hope is you guys. I saw an Thread a guy had the same problem here 10 years ago with his 1990 LS400 but he didnt write what was the main problem!
Please help me guys.
Thank you

Replace batteries in the remote. When the alarm is triggered, press lock or unlock and it should deactivate.

I already tried!
I changed the Batterie but didnt work!

Is it possible to reprogram the 1993 SC400 key?

German dude,


Have you tried inserting the key into the driver-side lock and turning if left to activate the alarm? Then remove the key, re-insert it, and unlock the door by turning to the right. That's how it works on my '95. Is your alarm a third-party add-on or the Toyota/Lexus factory alarm? I thought the factory remote alarm key wasn't available until 1996 but I could be wrong.




.

My Alarm is Original From Toyota/Lexus and i tried all the things what you said but it doesnt work!
How can i disable the Alarm!?
I dont need it! I just have trouble now

German dude,


I would disconnect the battery and wait half an hour. Reconnect the battery and try locking the car manually with the master key. Then try unlocking.



It's worth a try...

I already tried this!
Anytime i reconnect the battery then the Alarm starts again and the only way to turn it off is to try to start the engine but it doesnt work :-(

might be a failing ecu.

I think so too!
Because i tried everything!!
I ordered new ECU from ebay!
I can change it? Or i habe to reprogram it?
I thought maybe something wrong with the Lock? Door locks or trunk lock? What do you think?

Disconnect the alarm module connector and see if that helps. It is behind the rear passenger quarter panel or pull the fuse for the security system. It is worth a try if you haven't already tried that.

Alright! I will try it!
Where is the fuse?

My Central lock doesnt work!
I think thats the reason why the car wont start!
The Alarm deactivate only if the central lock opens, is that correct?

I would also love to know what fuse this would be! :)

The key lock switch is the problem. I just took one apart and cleaned it and have not tried it yet.

You have to put the key in the drivers side door, turn the key twice to the right and twice to the left.

So right, right, left, left

And possibly right, right, left, left again. I forget.

Then just get into the car, close the door behind you and start the car.

Done!!

1st Gen. SC400 Disabling Anti Theft Issue
 

For anyone having the same issue I had to disconnect Negative battery cable, clip some wires under the dash and ReWire mine. But a quick trick to start the engine and bypass the anti theft ( this takes two people ) is to disconnect the negative cable - get into the car set the key to the on position. ( turn key to the right just before ignition ) - then at the same time place negative cable back down and turn key to ignition simultaneously this should start the car but will only have bypassed the anti theft system .

Hey man. Just picked up an 93 sc400 yesterday and I set off the alarm when I brought it home and have this same issue. No key fob. And it’s not the og key but I started the car no problem a couple days ago when I first checked out the car. Can you point me in the right direction of said wires ? I need to get around this stupid ass alarm system so I can start the car without having to throw on the negative cable while the keys turned.