DOES NOT MEET STATE EMISSION TESTING AT IDLE

Some 1985-86 S/T trucks or M vans with 2.5L engines and manual transmissions may experience difficulty meeting the hydrocarbon (HC) exhaust emission requirements of state inspection maintenance test programs. If this condition cannot be corrected using the service procedures in Section 6E-Engine Emissions of the appropriate service manual, the following service PROMs are available from GMSPO to repair the condition. Use the PROM replacement procedure in Section 6E-Engine Emissions for PROM replacement.

Service Rear PROM Model Engine Transmission Axle Tire Size ---- ----- ------ ------------ ---- --------- 1228389 M Van 2.5L (LN8) 4-Spd Man (MR2) 3.42 (GU6) All

1228390 M Van 2.5L (LN8) 4-Spd Man (MR2) 3.73 (GT4) All

1228391 M Van 2.5L (LN8) 4-Spd Man (MR2) 4.10 (GT5) All

1228392 M Van 2.5L (LN8) 5-Spd Man (ML3) 3.73 (GT4) All

1228393 M Van 2.5L (LN8) 5-Spd Man (ML3) 4.10 (GT5) All

1228381 S Pickup/ 2.5L (LN8) 4-Spd Man (M73) 3.73 (GT4) All Extended Cab

1228385 S Blazer/ 2.5L (LN8) 4-Spd Man (M73) 3.73 (GT4) All Jimmy 4-Spd Man (M73) 3.73 (GT4) All

T(All) 2.5L (LN8) 4-Spd Man (MC9) 3.73 (GT4) All 4-Spd Man (M73) 4.11 (HO4) P235/ 75RI5 1228386 S Blazer/ 2.5L (LN8) 4-Spd Man (MC9) 4.11 (HO4) All Jimmy 4-Spd Man (M73) 4.11 (HO4) All T(All) 2.5L (LN8) 4-Spd Man (MC9) 4.11 (HO4) All 4-Spd Man (M73) 4.11 (HO4) All Tires Except P235/75Rl5

1228382 S Longbed 2.5L (LN8) 4-Spd Man (M73) 4.11 (HO4) All Pickup

1228383 S (All) 2.5L (LN8) 5-Spd Man (ML3) 3.73 (GT4) All

1228384 S Pickup/ 2.5L (LN8) 5-Spd Man (ML3) 4.11 (HO4) All Extended Cab

1228388 T (All) 2.5L (LN8) 5-Spd Man (ML2) 4.11 (HO4) P235/ 75R15 1228387 S Blazer/ 2.5L (LN8) 5-Spd Man (ML3) 4.11 (HO4) All Jimmy

1228353 S (All) 2.5L (LN8) 4-Spd Man (M73) 3.42 (GU6) All

The following codes identify specific transmissions.

NOTICE: Borg Warner transmissions used in S/T trucks can be identifted by the separate bell housing to transmission. Isuzu transmissions are a complete assembly.

MC9 - Borg Warner 4 Speed ML2 - Borg Warner 5 Speed ML3 - Borg Warner 5 Speed MR2 - Muncie 4 Speed M73 - Isuzu 4 Speed

Use applicable Labor Time and Operation Numbers.

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.