1994 E350, trying to track down transmission issues. It is shifting really hard, and OD light is flashing steady constantly. OD still works, and button still turns it on/off. RABS light is also on. Trans shop told previous owner it was almost definitely the VSS, I replaced that, and it seems slightly better, but it is still not right. How can I pull the trouble codes for this? I hear there is a procedure that should flash them on the OD light?