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 pre-programmed in the engine control module (ECM) 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 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).

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

HINT: When λ deviates from 1, the short-term fuel trim initially compensates at every engine speed (RPM) / load range (idling speed, lower part load and upper part load). The diagnostic trouble codes (DTCs) are erased, the adaptation values are reset. This means fuel trim will be high or low when driving in the low engine speed/load ranges before the trim is complete. For more information about fuel trim, see VADIS Design and Function, Fuel trim. Requires Volvo scan tool.