Long-term fuel trim bank x, upper part load

Measurement range 0-2.

Multiplicative adaptation of short-term fuel trim - adaptation occurs at upper partial load (high speed/acceleration on the road). The value stored in the Engine control module (ECM) indicates how much the short-term fuel trim has been corrected in the upper partial load range so that the short-term fuel trim value can once again be around 1 at upper partial 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 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 "long-term fuel trim" returns to 1. For more information about fuel trim, see VIDA Design and Function, Fuel trim. Requires Volvo scan tool.