NHTSA Engineering Analysis EA02028

ODI OPENED EA 02-028 TO REVIEW COMPLAINTS OF CONSUMERS REPORTING THAT THEIR FUEL GAUGE WAS INCORRECTLY DISPLAYING THE AMOUNT OF FUEL IN THE GAS TANK.THE FUEL GAUGE RECEIVES AN ELECTRICAL SIGNAL FROM A FUEL TANK SENDING SENSOR CIRCUIT CARD.A FLOAT ARM IN THE TANK MOVES ELECTRICAL CONTACTS THAT RUB AGAINST THE CARD AS THE LEVEL OF FUEL RISES AND FALLS.DISRUPTION OF THE ELECTRICAL SIGNAL (SUCH AS CAUSED BY CORROSION OF THE CIRCUIT CARD) WILL CAUSE INCORRECT READINGS TO REGISTER ON THE FUEL GAUGE.GM REPORTED IN THEIR RESPONSE TO ODI DATED JANUARY 13, 2003 THAT THE PRIMARY CAUSE OF ERRATIC FUEL GAUGE OPERATION IS EXCESS ELEMENTAL SULFUR IN FUEL.GM REPORTED THAT ABNORMAL LEVELS OF SULFUR SPORADICALLY OCCURRED IN CERTAIN PARTS OF CANADA AND THE U.S. RESULTING IN REPORTS OF FUEL GAUGE MALFUNCTION.GM MODIFIED THE SENDING SENSOR FOR VEHICLES BUILT AFTER OCTOBER 2000.IT MADE A SECOND SENSOR MODIFICATION FOR VEHICLES BUILT AFTER JANUARY 2003.GM ALSO ISSUED A CUSTOMER SATISFACTION CAMPAIGN (GM NUMBER 00101) IN DECEMBER 2000 FOR U.S. CUSTOMERS IN THE STATE OF MAINE AND ISSUED SEVERAL SERVICE BULLETINS INFORMING DEALERS OF THE AVAILABILITY OF SENSORS WITH IMPROVED CORROSION RESISTANCE.THE COMPLAINT TREND INDICATES THAT COMPLAINTS PEAKED IN LATE 2000 TO EARLY 2001.WARRANTY CLAIMS DECLINED SINCE PEAKING IN APRIL 2002.BASED ON THE NUMBER OF COMPLAINTS AND THE INDICATION OF A DECLINING TREND, FURTHER USE OF AGENCY RESOURCES DOES NOT APPEAR TO BE WARRANTED.THE CLOSING OF THIS INVESTIGATION DOES NOT CONSTITUTE A FINDING BY NHTSA THAT NO SAFETY-RELATED DEFECT EXISTS.THE AGENCY RESERVES THE RIGHT TO TAKE FURTHER ACTION IF WARRANTED BY THE CIRCUMSTANCES.