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LTFT and STFT were converging to a new value: conditions have changed, so STFT was not aligned with LTFT direction, and eventually all settled to approx 0%.


Long Term Fuel Trim (LTFT) should respond over time; in a process called 'Block Learn' by many manufacturers; to systemic changes in the operating conditions of the engine. For example, a change in fuel vendors, a change in regular operating altitude. Short term fuel trim will respond to rapid, transient changes in operation, such as gas pedal, hill grade ...


No, it shouldn't. During a remap, there are tables which the ECU reads to know what/when/how fueling and other events should occur. This is in non-volatile memory. There are other parts of the ECU which will be wiped out, such as error codes and the fine adjustments the vehicle does to itself to get the tune "just right", which is in volatile ...

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