CHIRP NOISE FROM INJECTION REACTION SYSTEM AT IDLE

* VEHICLES AFFECTED: 1988 C/K 10-30 TRUCKS WITH 5.0L AND 5.7L

Some 1988 C/K 10-30 trucks may have been built with incorrect Air Injection Reaction System (A.I.R.) check valves and may experience a belt chirping noise at idle. This condition may be diagnosed by disconnecting the A.I.R. hoses at the check valves and repeating the condition at which the noise occurred. If the noise is eliminated, the A.I.R. hoses should be reconnected and the check valves should be replaced with check valve, P/N 22050642.

Labor Op: J6090 - Valve, Air Check Replace, Right Side .2hr J6091 - Valve, Air Check Replace, Left Side .2hr

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.