2002 Lexus SC
Key Replacement - Save vs Dealer in Ventura County

2002 Lexus SC Remote Head Key Replacement - Fast, Affordable & Professional

Out near Chesebro Canyon Trail in Simi Valley, a guy with a 2002 SC 430 flagged me down through a referral. He had already paid another locksmith full price for a replacement key that never actually worked. The engine would crank for about two seconds, then the immobilizer cut fuel and the security light on the dash stayed solid. The first locksmith told him his smart ECU was bad and left.

The ECU was fine. What happened is the other tech rushed the transponder registration. The Lexus immobilizer on these uses a timed seed/key security handshake through the 89780-24010 module, and if you skip ahead or interrupt the countdown, the key writes temporarily but never commits to permanent memory. The car sees it once, then forgets it.

I ran my TOY43 Lishi to verify the blade cut matched the wafers. Connected through OBD, cleared the partial registration, and started a clean key learn with the full timed sequence. No shortcuts. The HYQ12BBK wrote to permanent memory, and I confirmed it on the Autel IM608 screen. Three consecutive start tests, three clean starts, no security light.

He had already paid someone else for a key that did nothing. I made sure this one actually held. He stood there watching the dash the whole third start like he was waiting for it to fail again. It did not.

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