NHTSA Engineering Analysis EA06016

IN A LETTER DATED NOVEMBER 7, 2007, GENERAL MOTORS (GM) REPORTED TO THE OFFICE OF DEFECTS INVESTIGATION (ODI) THAT IT WILL CONDUCT A SAFETY RECALL (07V-521) TO REPLACE THE CRANK POSITION SENSOR (CKP) IN APPROXIMATELY 12,000 MODEL YEAR (MY) 2001 CHEVROLET SILVERADO AND GMC SIERRA VEHICLES EQUIPPED WITH 8.1 LITER ENGINES MANUFACTURED ON OR BEFORE NOVEMBER 15, 2000.ACCORDING TO GM, THE CKP CAN FAIL INTERMITTENTLY OR PERMANENTLY.A PERMANENT CKP FAILURE WOULD RESULT IN AN ENGINE STALL WITHOUT RESTART.AN INTERMITTENT CKP FAILURE COULD CAUSE THE SERVICE ENGINE SOON LIGHT TO ILLUMINATE, THE VEHICLE TO RUN ROUGH OR THE ENGINE TO STALL BUT ALLOWS RESTART.AS A REMEDY, AN IMPROVED CKP WILL BE INSTALLED IN THE SUBJECT VEHICLES.THE RECALL CAMPAIGN WILL START IN DECEMBER 2007. DURING THE PRELIMINARY EVALUATION (PE06-016), AND THIS EA INVESTIGATION, GM AND ODI INDEPENDENTLY CONDUCTED DETAILED REVIEWS OF CERTAIN FIELD DATA TO UNDERSTAND THE NATURE AND RATE OF SUBJECT VEHICLE STALLING DUE TO CKP FAILURES.GM AND ODI REVIEWED GM'S WARRANTY CLAIMS FOR THE CKP WITH THE OBJECTIVE OF ASCERTAINING AN ESTIMATE OF THOSE CLAIMS REPRESENTING AN ENGINE STALL WHILE DRIVING.THE CKP WARRANTY CLAIMS WITHOUT VERBATIM TEXT WERE THE LARGEST SEGMENT OF WARRANTY CLAIMS.USING THOSE CLAIMS, GM SURVEYED VEHICLE OWNERS TO GATHER ADDITIONAL INFORMATION TO DETERMINE IF THE CLAIM WAS ASSOCIATED WITH A STALL WHILE DRIVING EVENT.BASED ON THE SURVEY, GM ESTIMATED THAT APPROXIMATELY 49% OF ALL WARRANTY REPAIRS FOR THE CKP INVOLVED A STALL WHILE DRIVING.ODI?S REVIEW OF GM'S SURVEY DATA PRODUCED A HIGHER ESTIMATE (71%) FOR STALL WHILE DRIVING.GM FURTHER ESTIMATED THE RATE OF STALL WHILE DRIVING FOR THE SUBJECT VEHICLES OVER TIME.IT ESTIMATED STALLING WHILE DRIVING RATES OF 1.6%, 4.6% AND 8.9% AT 1, 3 AND 6 YEARS IN SERVICE RESPECTIVELY.ODI'S REVIEW OF THE GM'S SURVEY DATA FINDS HIGHER ESTIMATED STALL WHILE DRIVING RATES OF 2.2%, 6.8% AND 13% AT 1, 3 AND 6 YEARS IN SERVICE RESPECTIVELY. ODI ALSO CONDUCTED A SURVEY OF