EXHAUST ODOR SUMMARY BULLETIN (PROMS)

Model and Year: 1986-88 M-VAN WITH 4.3L ENGINE

Some 1986-88 M-vans prior to JB191855, equipped with 4.3L (VIN Code Z) engines, may exhibit an exhaust odor often described as sulfur or rotten egg smell at idle following sustained highway driving or trailer towing.

This bulletin includes a table which summarizes the various service fixes intended to address this condition depending on the model year of the vehicle.

The table lists the appropriate service procedures, calibration PROM, applicable service parts and a bulletin number to reference for complete installation instructions.

VEHICLE DESCRIPTION S E R V I C E I N F O R M A T I O N -------------------- -------------------------------------

Serv. Mod. Axle Prom Prom PROM ID Bleed PN Year Emiss. Trans. Ratio Kit P/N Label Scanner (If Appl.) ---- ------ ------- ----- ------- ----- ------- ----------

1988 Fed A4 (MD8) All 16121142 AKMH 3051 N/A

M5 (MH3) All 16120722 AKSP 3561 N/A

Calif A4 (MD8) All 16121146 AKMJ 3061 N/A

M5 (MH3) All 16120727 AKSR 3571 N/A

1987 Fed A4 (MD8) All 16082087 AKDX 2261 10105820 M5 (MH3) 2.73 16088400 AMJL 8401 10105820 M5 (MH3) 3.08/3.42 16082103 AKFA 2291 10105820 Calif A4 (MD8) All 16088362 AMDA 8351 10105820 M5 (MH3) 2.73 16087025 AMBS 7261 10105820 M5 (MH3) 3.08/3.42 16087020 AMBR 7251 10105820

1986 Fed A4 (MD8) All 16068877 ACHJ 9081 10093100 M5 (MH3) 2.56/2.73 16068942 ACHL 9101 10093100 M5 (MH3) 3.08/3.42 16068952 ACHN 9121 10093100 Calif A4 (MD8) All 16068926 ACHK 9091 10093100 M5 (MH3) 2.56/2.73 16068946 ACHM 9111 10093100 M5 (MH3) 3.08/3.42 16068956 ACHP 9131 10093100

Y-Pipe & Mod. Axle Plug P/N Reference Year Emiss. Trans. Ratio (If Appl.) Bulletin ---- ------ ------- ----- ---------- --------

1988 Fed A4 (MD8) All Y-pipe 15598249 Plug 10017198 Chev 88-255-6E M5 (MH3) All Y-pipe 15598249 Plug 10017198 Calif A4 (MD8) All Y-pipe 15598249 Plug 10017198 Chev 88-255-6E M5 (MH3) All Y-pipe 15598249 Plug 10017198

1987 Fed A4 (MD8) All N/A M5 (MH3) 2.73 N/A Chev 88-235-6E M5 (MH3) 3.08/3.42 N/A Calif A4 (MD8) All N/A M5 (MH3) 2.73 N/A Chev 88-235-6E M5 (MH3) 3.08/3.42 N/A

1986 Fed A4 (MD8) All N/A M5 (MH3) 2.56/2.73 N/A Chev 86-253-6E M5 (MH3) 3.08/3.42 N/A Calif A4 (MD8) All N/A M5 (MH3) 2.56/2.73 N/A Chev 86-253-6E M5 (MH3) 3.08/3.42 N/A

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.