Long-term fuel trim bank x, idle speed (%)

Measurement range: between -72 and +72%.

Additive adaptation of the short-term fuel trim (correcting the injection period), adaptation that occurs at idle speed. The value indicates how much the short-term fuel trim has been corrected at idle speed so that the short-term fuel trim value can again oscillate around 1.

In the event of an air leakage for example, the value will increase at idle speed (= longer injection time). This is to compensate the fuel / air mix for air capacity. Regardless of the load /engine speed, the same injection time is added. This means that the parameter value does not significantly affect the fuel / air mix at higher loads / engine speeds.

Normal value when the engine is idling: 0 ± 5%.

Value over 0%: the control module increases the injection period (to prevent a lean fuel / air mix).

Value less than 0%: the control module decreases the injection period (to prevent a rich fuel air mix).

HINT: When diagnostic trouble codes (DTCs) are erased, the adaptation returns to 0%. For more information about fuel-trim adaptation, see VIDA Design and function, Fuel trim. Requires Volvo scan tool.