The tuner repurposes an unused pin on the ECU connector — often pin 18 or 70 on the 121-pin EDC15P/EDC15V — for mode switching. You connect this pin to:
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Normally, an ECU holds a single calibration for engine operation. An setup modifies the internal logic to store and switch between multiple "datablocks". Historically, Bosch designed these ECUs with three codeblocks to handle different vehicle variants—such as Manual, Automatic, or 4x4 transmissions. The tuner repurposes an unused pin on the