Long-Term Fuel Trim Bank X, Upper Part Load

Measurement range 0-2.

Multiplicative adaptation of the short-term fuel trim, adaptation that occurs at the upper part load (high speed / acceleration on the road). The value stored in the engine control module (ECM) indicates how much the short-term fuel trim in the upper part load range has been corrected so that the short-term fuel trim value can again oscillate around 1 at the upper part load.

In the event of low fuel pressure for example, the value will increase (= longer injection time). This is to compensate the fuel/air mix for the lack of fuel.

Normal value 1 ± 0.1. The upper part load range of the engine must be reached for the value to be updated (accelerating road driving).

Approximately 30 minutes of driving in the upper part load may be required before the adaptation is complete (complete = short-term fuel trim oscillates around 1 at upper part load).

Value over 1: The engine control module (ECM) increases the injection period (to prevent a lean fuel / air mix).

Value under 1: The engine control module (ECM) decreases the injection period (to prevent a rich fuel / air mix).

HINT: When diagnostic trouble codes (DTCs) are erased, the adaptation returns to 1.