Is there power to the ACC at all? Do you hear the aspirator motor or vent pods as you switch modes? IIRC the wires to the porcupine go through a junction block by the cowl beside the brake booster. Power, ground and a yellow(?) signal wire. This is from the deep recesses but the signal is 0-5V or 0-7V which the porcupine translates to a PWM signal to the motor. I’d start at that junction block.

Sixto
98 E320s sedan and wagon