Long-term fuel trim bank x, idle speed

Measurement range from -72 to +72 %.

Additive fuel trim (correcting the injection period), trim that occurs at idle speed. The value indicates how much the fuel trim has been corrected at idle speed so that the 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 under 0 %: 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 0%. For more information about fuel-trim, see VIDA Design and Function, Fuel trim. Requires Volvo scan tool.