Engine controller and associated operating method

[0024]The block circuit diagram in FIG. 1 shows a control unit 1 according to the invention, which is used in an electronic engine controller for a spark ignition engine in order to disable a lean mode of the spark ignition engine if the spark ignition engine is to change over into another operating mode. The control unit 1 therefore has a binary signal output for disabling or respectively enabling the lean mode, a control signal OUT being output at said signal output and the control signal OUT assuming a high level to disable the lean mode and a low level to enable the lean mode.

[0025]The lean mode is disabled, for example, if an activated carbon filter has to be regenerated in the fuel tank venting operation. For this purpose, the control unit 1 has an evaluation unit 2 which is illustrated in detail in FIG. 2 and picks up, at the input end, a previously determined degree of loading CL of the activated carbon filter and a measured time period T_CL since the last regeneration of the a