Short-term fuel trim, bank x

Measurement range 0-2.

The value displays how much the injection period needs to be corrected (from the preprogrammed injection period in the control module) to reach λ=1. If the engine runs lean or rich (λ deviates from 1), the short-term fuel trim injection period is increased or decreased so that λ; =1. The average value of this parameter from different engine speed and load ranges is used for the different fuel trim adaptations (idling, lower part load and upper part load) so that the short-term fuel trim is always around 1.

Short-term fuel trim = the actual injection period required to reach λ=1, divided by (/) the injection period in preprogrammed in the control module to reach λ=1.

The normal value oscillates around 1, when fuel trim for each engine speed (RPM) / load range is ready.

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).

The parameter must be checked under stable conditions, such as stable engine speed (RPM) and load.

HINT: When λ deviates from 1, "short-term fuel trim" initially compensates at each engine speed/load range (idle, lower part load and upper part load). When diagnostic trouble codes (DTCs) are erased, the values for "short-term fuel trim" are reset, this means that "short-term fuel trim" becomes too high or low when driving at relevant engine speed/load range before fuel trim is complete. For further information about fuel trim, see VIDA Design and function, Fuel trim. Requires Volvo scan tool.