Think City Programming Failure Due to Incorrect Transponder Bit-Depth

This cause is confirmed by comparing the physical specifications of the 4D63 chip to the vehicle's requirement for either 40-bit or 80-bit encryption. The failure is verified when the diagnostic tool successfully initiates the handshake sequence but reports an 'Incorrect Key' or 'Programming Failed' error during the final write cycle. Confirm the correct part number (e.g., 98AG15K601AC) matches the vehicle's specific immobilizer module requirements, as the ECU will reject any chip that does not match the expected bit-depth formatting.

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