Long-Term Fuel Trim Bank X, Upper Part Load

Measurement range 0-2.

Multiplicative fuel trim, trim that occurs at the upper part load (high speed / acceleration on the road). The value stored in the control module indicates how much the fuel trim in the upper part load range has been corrected so that the 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 lower part load may be required before the fuel trim is complete (complete = fuel trim oscillates around 1 at upper part load).

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

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

HINT: When diagnostic trouble codes (DTCs) are erased, the "long-term fuel trim" returns to 1.