INFO. ON ENHANCED EMISSION INSPECTION MAINTENANCE PROGRAM. Chevrolet Chevy MD P Bus Chassis 1988

SUBJECT: INFORMATION ON ENHANCED EMISSION INSPECTION MAINTENANCE PROGRAM - REPAIR CONFIRMATION EQUIPMENT PERFORMANCE

MODELS: 1996 AND PRIOR PASSENGER CARS AND TRUCKS

THIS BULLETIN SUPPLEMENTS INFORMATION REGARDING REPAIR CONFIRMATION EQUIPMENT PROVIDED IN PREVIOUS BULLETINS DISCUSSING ENHANCED EMISSION PROGRAMS (CORPORATE BULLETIN NUMBER(S) 43-65-05, 43-65-07, 43-65-10 AND 53-65-07).

STG CONTINUES TO RECOMMEND THAT NO ADDITIONAL ENHANCED EMISSIONS INSPECTION EQUIPMENT BE PURCHASED BEYOND THE DIAGNOSTIC PRODUCTS INCLUDED IN THE ESSENTIAL TOOL PROGRAM. AN EXTENSIVE STUDY HAS BEEN COMPLETED BY STG TO IDENTIFY ANY PRODUCTS/EQUIPMENT THAT COULD BE USED TO VERIFY THE EFFECTIVENESS OF THE DIAGNOSIS AND REPAIRS MADE. THE OBJECTIVE OF THE STUDY WAS TO IDENTIFY ANY PROCESS(ES), PREFERABLY LOW COST, WHICH WAS CAPABLE OF PREDICTING IM240 TEST RESULTS BEFORE RETURNING THE VEHICLE FOR RETEST AT A CENTRALIZED TEST FACILITY. MORE SPECIFICALLY, THE GOAL WAS TO IDENTIFY ANY TEST EQUIPMENT/PROCEDURES CAPABLE OF ACHIEVING ACCEPTABLE LEVELS OF CORRELATION AND PREDICTION INTERVALS WITH THE IM240 TEST. CORRELATION IS A STATISTICAL TERM MEANING THE MEASURE OF THE STRENGTH OF THE RELATIONSHIP BETWEEN THESE EQUIPMENT/PROCEDURES AND THE IM240 TEST ITSELF, WHILE THE PREDICTION INTERVAL PREDICTS THE RANGE OF PERFORMANCE (IM240 TEST RESULTS) THAT COULD RESULT WHEN USING THESE EQUIPMENT/PROCEDURES. THE RESULTS OF THE STUDY INDICATED THAT NONE OF THE EQUIPMENT/PROCEDURES EVALUATED WERE CAPABLE OF MEETING EITHER THE CORRELATION OR PREDICTION INTERVAL STANDARDS.

EQUIPMENT INCLUDED IN THIS STUDY INCLUDED RG240 SYSTEMS (DYNAMOMETER, CONSTANT VOLUME SAMPLER, AND GAS ANALYSIS), PORTABLE GAS ANALYZERS USED TO MONITOR THE EXHAUST UNDER STATIC AND DRIVING CONDITIONS, AS WELL AS COMBINATIONS OF BOTH STATIONARY AND PORTABLE EQUIPMENT. WHILE WE HAVE YET TO IDENTIFY A SATISFACTORY PROCESS FOR VERIFYING ENHANCED EMISSION REPAIR EFFECTIVENESS IN GM DEALERSHIPS, WE HAVE LEARNED THAT STRICT ADHERENCE TO THE STRATEGY BASED DIAGNOSTIC PROCEDURES (FOUND IN THE ENHANCED INSPECTION MAINTENANCE DIAGNOSTIC MANUAL), COUPLED WITH THE USE OF THE ESSENTIAL EQUIPMENT, WILL ENSURE SATISFACTORY PERFORMANCE AT THE CENTRALIZED IM240 TEST FACILITY. IN MOST ALL CASES, THE VEHICLES INVOLVED IN THE FOREMENTIONED STUDY WERE CORRECTLY REPAIRED AND SUCCESSFULLY PASSED THEIR RETEST THE FIRST TIME. THE BEST WAY TO ENSURE THAT YOU ARE ADEQUATELY PREPARED TO PERFORM ENHANCED IM240 EMISSIONS REPAIRS IS TO ENROLL IN TRAINING COURSE #16004.10 "VEHICLE EMISSIONS, ENHANCED TESTING AND REPAIR".

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GENERAL MOTORS BULLETINS ARE INTENDED FOR USE BY PROFESSIONAL TECHNICIANS, NOT A "DO-IT-YOURSELFER". THEY ARE WRITTEN TO INFORM THOSE TECHNICIANS OF CONDITIONS THAT MAY OCCUR ON SOME VEHICLES, OR TO PROVIDE INFORMATION THAT COULD ASSIST IN THE PROPER SERVICE OF A VEHICLE. PROPERLY TRAINED TECHNICIANS HAVE THE EQUIPMENT, TOOLS, SAFETY INSTRUCTIONS AND KNOW-HOW TO DO A JOB PROPERLY AND SAFELY. IF A CONDITION IS DESCRIBED, DO NOT ASSUME THAT THE BULLETIN APPLIES TO YOUR VEHICLE, OR THAT YOUR VEHICLE WILL HAVE THAT CONDITION. SEE A GENERAL MOTORS DEALER SERVICING YOUR BRAND OF GENERAL MOTORS VEHICLE FOR INFORMATION ON WHETHER YOUR VEHICLE MAY BENEFIT FROM THE INFORMATION.