For 1990-2009 cars

# ALTITUDE REQUIREMENTS ADJUSTMENT INFORMATION

NEW FEDERAL EMISSIONS REGULATIONS APPLICABLE TO 1982 MODEL YEAR VEHICLES CONTAIN REQUIREMENTS FOR VEHICLES SOLD FOR PRINCIPAL USE IN DESIGNATED HIGH ALTITUDE AREAS. (SEE ATTACHED LIST OF DESIGNATED HIGH ALTITUDE AREAS). THESE VEHICLES MUST CONFORM TO HIGH ALTITUDE EMISSIONS REQUIREMENTS. IN ADDITION, THERE ARE REGULATIONS WHICH REQUIRE MANUFACTURERS TO PROVIDE RECOMMENDED IN-USE ADJUSTMENTS TO IMPROVE PERFORMANCE, WHEN APPLICABLE, FOR VEHICLES THAT CHANGE PRINCIPAL USE AFTER SALE FROM EITHER LOW TO HIGH, OR HIGH TO LOW, ALTITUDE. THIS BULLETIN IS INTENDED AS A GUIDE FOR DETERMINING WHICH VEHICLES MAY BE LEGALLY SOLD FOR PRINCIPAL USE AT HIGH ALTITUDE, WHICH VEHICLES CAN AND MUST BE MODIFIED PRIOR TO SALE IF SOLD FOR PRINCIPAL USE AT HIGH ALTITUDE, AND WHICH VEHICLES MAY BE MODIFIED AFTER SALE FOR IMPROVED PERFORMANCE WHEN PRINCIPAL USE IS CHANGED FROM HIGH TO LOW, OR LOW TO HIGH, ALTITUDE. IT IS CRITICAL THAT VEHICLES BE DELIVERED TO THE CUSTOMER WITH THE PROPER EMISSION SYSTEM CONFIGURATION TO ENSURE COMPLIANCE WITH APPLICABLE EMISSIONS REGULATIONS AND TO PROVIDE MAXIMUM CUSTOMER SATISFACTION. CHEVROLET OFFERS TWO (2) FEDERAL ALTITUDE EMISSION PACKAGES AS THE FOLLOWING RPO'S: NA5 = DESIGNED FOR ALL ALTITUDE USE WHEN NA6 IS NOT AVAILABLE OR LOW ALTITUDE ONLY WHEN NA6 IS AVAILABLE. NA6 = DESIGNED FOR HIGH ALTITUDE USE. SOME CHEVROLET VEHICLES MAY BE CONVERTED FROM ONE OF THESE CERTIFIED CONFIGURATIONS TO ANOTHER USING THIS BULLETIN AS A GUIDE. GASOLINE ENGINE CONFIGURATIONS NOT SHOWN ON THE ATTACHED LIST ARE NOT MODIFIABLE. TEXT * * SEE BULLETIN FOR TEXT *

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.