E90 is a communication error between the main control pcb and the display pcb in the fascia.Take the lid off and there is a blue loom with 5 wires that goes from the main pcb to the display pcb.if the connections become bad this error code comes up.disconnect the blue loom at both ends and tighten the connections and clean the display pcb edge connection.reconnect blue wire and test.if error still persists try a new blue loom,new main pcb or new display pcb.usually its bad connections from this blue loom
ck, December 2011
