My Suzuki will not go into 4WD. My mechanic says there's an error code saying there is no communication from the control module to the 4WD. The actuator on the the differential checked out as ok. After following the flowchart to check the wiring, it was determined the wiring is fine and the control module was the problem. They put in a new control module and the same error is there. Do you have any idea what else the problem could be?