Short Term

Short Term Adaptive or Short Term Fuel Trim (STFT) is an immediate correction to fuel injector pulse width. During Closed Loop operation, Short Term Adaptive makes immediate adjustments to fuel delivery in direct response to the signal from the upstream oxygen sensor. The PCM infers air/fuel ratio by monitoring oxygen content measured by the upstream oxygen sensor.

This is an immediate response to the oxygen sensor signal that is consistently high or low. The PCM knows that the base pulse width calculation needs to be modified by adjusting the injector pulse width until the correct oxygen sensor voltage is achieved. The need to adjust the injector pulse width may be a result of vehicle operating conditions, engine wear, fuel quality, etc. The maximum range of authority for Short Term Adaptive is ±33%. Short Term Adaptive values are not stored when the ignition is off.