Think City Failure to Program 4D63 Transponder

Confirmation of the programming failure is identified by the vehicle's refusal to start after an attempt to register a new key. The primary indicator is a flashing or solid security light (lock/key icon) on the instrument cluster, signaling that the Immobilizer Control Unit (ICU) has rejected the transponder's handshake signal. The vehicle will typically enter a locked state where the ignition is engaged but the motor controller remains disabled.

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