Bypassing the operating code system?

What is it you are attempting to do or are asking if it's possible to do?

How can the immobilizer (security code) on a diesel Kia Sportage be bypassed?

It cannot be bypassed. The newer vehicles use a much more sophisticated system than the vehicles of the past. They use multiple modules to verify the security items and tampering can brick the vehicle. What is the problem you have?

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What is the reason you want to bypass the security system? Vehicle doesn't start, starts and shuts off ? For those there is limited testing to repair the problem, like replacing a receiver antenna or testing to see if it's a failed transponder and returning the system to operation. However if you are trying to disable the system, it cannot be done without having access to the actual coding in the ECU and security system software, and you would need to change other programming as well because there are multiple modules that need to verify the security system is operating before the vehicle will run.

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Not sure what you are saying here.