NHTSA Preliminary Evaluation PE99063

ODI HAS EXPANDED THE SCOPE OF ITS INVESTIGATION OF STEERING COLUMN FIRES TO INCLUDE ALL MODELS BUILT ON THE N-PLATFORM.GM HAS INDICATED IN ITS RESPONSE THAT THE SUBJECT VEHICLES ARE EQUIPPED WITH A ROTARY IGNITION SWITCH THAT HAS BEEN IN USE IN A NUMBER OF VEHICLE MODELS SINCE 1991 ON BOTH THE N AND J-PLATFORMS.HOWEVER, THE 1994-1995 N-PLATFORM IS OVER REPRESENTED ACCOUNTING FOR 83 (81%) OF THE COMBINDED TOTAL OF 102 REPORTS DESPITE BEING ONLY 14.2% OF THE COMBINED POPULATION. OF THE 10 NEW REPORTS RECEIVED SINCE OPENING EA99-063, 7 INCLUDE ALLEGATIONS OF A NO START CONDITION WHEN ATTEMPTING TO ENGAGE THE STARTER.A FIRE IS CLAIMED TO HAVE ENSUED IN THE STEERING COLUMN IMMEDIATELY THERAFTER.GM ISSUED A TECHNICAL SERVICE BULLETIN (TSB) (NO. 433203) JULY 1994 WHIICH ADDRESSED OWNER COMPLAINTS THAT THE IGNITION SWITCH MAY NOT RETURN TO THE RUN POSITION AFTER THE VEHICLE HAS STARTED.THE TSB ADVISES THAT THE IGNITION SWITCH MOUNTING SCREWS MAY BE EXCESSIVELY TORQUED RESULTING IN DISTORTION OF THE SWITCH HOUSING.AN ENGINEERING ANALYSIS IS WARRANTED TO DETERMINE THE ROOT CAUSE(S) AND TO DETERMIN IF A SAFETY DEFECT EXISTS.