ABS TONE RING CORRODES CAUSING UNINTENDE

ODI INITIATED PE02-061 BASED ON TWO REPORTED INCIDENTS IN WHICH FREIGHTLINER VEHICLES EQUIPPED WITH "INTEGRAL" ABS TONE RINGS HAD EXPERIENCED INCREASED VEHICLE STOPPING DISTANCE. "INTEGRAL" TONE RINGS INCORPORATE THE ABS TONE RING INTO THE BRAKE ROTOR TO FORM A ONE-PIECE "INTEGRATED" COMONENT. FREIGHTLINER HAS IDENTIFIED 266 WARRANTY CLAIMS FOR CORRODED ROTORS. SINCE THE ABS TONE RING IS AN INTEGRAL PART OF THE HYDRAULIC BRAKE ROTOR IN THE AFFECTED FREIGHTLINER VEHICLES, CORRODED ROTOR SENSOR TEETH MAY COMPROMISE THE QUAILITY OF THE ABS TONE RING SIGNAL TO THE ABS ECU. A SIGNIFICANT NUMBER OF FREIGHTINER WARRANTY CLAIMS INDICATE THAT HE TONE RING CONDITION WAS DISCOVERED BY SERVICING MECHANICS WHO WERE INVESTIGATING THE CAUSE FOR THE ILLUMINATED ABS WARNING LIGHT. ODI IS CONCERNED AS TO (1) WHETHER VEHICLE OPEERAOTRS ARE SUFFICIENTLY COGNIZANT OF THE IMPORTANCE OF HAVING THE VEHICLE SERVICED IN A TIMELY MANNER IN RESPONSE TO THE ILLUMINATED ABS WARNING LIGHT SINCE THE ABS WARNING LIGHT IS THE ONLY WARNING PROVIDED BEFORE THE VEHICLE STOPPING DISTANCE MAY BE AFFECTED AND (2) QUANTIFYING THE EXTENT TO WHICH STOPPING-DISTANCE IS AFFECTED AND ASSESSING THE ASSOCIATED RISK TO SAFETY. ODI CONDUCTED A PARALLEL INVESTIGATION (PE02-060) OF INCREASED STOPPING DISTANCE ASSOCIATED WITH CORRODED ABS TONE RINGS AT INTERNATIONAL TRUCK. THIS INVESTIGATION WAS CONCLUDED ON NOV 21, 2002 AFTER INTERNATIONAL TRUCK CONCLUDED THAT THE "ABS ECU....CAN MISINTERPRET FALSE WHEEL SPEED SIGNALS..." AND NOTIFIED NHTSA OF THEIR INTENTION TO CONDUCT A CAMPAIGN (NHTSA 02V-252) TO CORRECT THE AFFECTED VEHICLES. RECOMMENDATION IS TO OPEN AN ENGINEERING ANALYSIS.