ALTITUDE EMISSION REQUIREMENTS AVAILABILITY AND ADJUSTMENTS

Federal emissions regulations applicable to 1983 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 emissions 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.

VEHICLE EMISSION CONTROL INFORMATION UPDATE LABELS

One of the labels identified by part number below must be affixed to the vehicle whenever a vehicle is adjusted and/ or modified using this bulletin.

The label should be ordered as regular parts and accessories through the Warehousing and Distribution Division of General Motors system. When ordering these labels via rapid entry, use order type CSD. Orders also may be placed on a PC66 and mailed directly to WDDGM, 6060 West Bristol Road, Flint, Michigan 48554, attention Ship Direct Department.

The label should be affixed in a readily visible position in the engine compartment and where possible beside the existing Emission Control Information (Tune-Up) label and should not be affixed to any equipment that can be easily detached from the vehicle.

Prior to installation of this label, the dealer code number and date of modification must be typed (with or without ribbon) or lettered with ballpoint pen in the space provided.

P/N 14042590

Low altitude vehicle converted for operation at high altitude prior to sale.

P/N 14057201

Low altitude in-use vehicle modified for improved performance at high altitude.

P/N 14055121

High altitude vehicle modified for improved performance at low altitude. (This label applies to in-use as well as prior to sale.)

PRIOR TO SALE ADJUSTMENTS VS. IN USE ADJUSTMENTS

Altitude adjustments on new vehicles prior to delivery to the customer for conformance to high altitude emissions standards are referred to in this bulletin as Prior-To-Sale Adjustments. Altitude adjustments on in-use vehicles for improved performance when there is a change of principal use from high altitude to low altitude or from low altitude to high altitude are referred to as Altitude Performance Adjustments of in-use modifications.

VEHICLE IDENTIFICATION

The "altitude status" of a particular vehicle may be verified by the Vehicle Emission Control Information (Tune-Up) Label. See Figure 1 and Figure 2 for label interpretations.

Use the following chart to determine what modifications, if any, are necessary to sell a specific vehicle.

Field Modification For High or Low Carline Engine/RPO Trans. Altitude

"J" 2.0L L46 All None Required All 2.5L LR8/L09 All None Required All 2.8L LE2/LH7 LC1/LL1 All None Required "G" 3.8L LC3 None Required All 5.0L LG4/LU5 All None Required All 5.7L LM1/L83 All None Required

LOW ALTITUDE VEHICLES WHICH MUST BE ADJUSTED PRIOR TO SALE FOR CONFORMANCE TO HIGH ALTITUDE EMISSIONS STANDARDS*

Field Modification For High Altitude Carline Engine/RPO Trans. Use

"T" 1.6L L17 All Install jumper wire from circuit #450E at ALDL connector to pin #18 on ECM connector.

*The above modifications which must be made prior to sale for conformance to high altitude emissions standards are the same as the in-use modifications which are recommended for improved performance for vehicles that after sale change principal use from low altitude to high altitude.

HIGH ALTITUDE VEHICLES WHICH MAY BE ADJUSTED FOR IMPROVED LOW ALTITUDE PERFORMANCE

Field Modification For Low Altitude Carline Engine/RPO Trans. Use

"T" 1.6L L17 All Remove circuit #450E from pin #18 on the ECM connector.

PROCEDURE FOR FABRICATING AND INSTALLING JUMPER WIRE

1. Attach a terminal, P/N 12004610, to each end of a 3 foot length of 16 or 18 gage wire.

2. Connect to pin #18 of the ECM.

3. Route wire along and in front of the dash panel.

4. Connect to ground terminal of the Assembly Line Diagnostic Link (ALDL).

HANDLING OF ALTITUDE ADJUSTMENT EXPENSE

Any required altitude adjustments on new vehicles prior to delivery to the customer for conformance to emission requirements in the area of principal use are the responsibility of the dealer.

IN-USE

Owners who move to high altitude counties

Dealers in high altitude areas should encourage owners who have moved to high altitude counties to have the Altitude Performance Adjustments performed on their vehicles as outlined in this bulletin. These adjustments/modifications are considered an owner maintenance expense.

Owners who move from high altitude counties

Dealers should advise owners moving to low altitude areas that they should have the Altitude Performance Adjustments performed on their vehicles as outlined in this bulletin. These adjustments/modifications are considered an owner maintenance expense.

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.