Subject: SERVICE MANUAL UPDATE-SEC. 6D4 SPARK PLUG CODING CHART
Model and Year: 1990 CORVETTE
Source: Chevrolet Service Bulletin
Bulletin Number: 90-253-6D - (06/26/1990)
The Spark Plug Coding Chart shown in Figure 2, Page 6D4-3, in Section 6D4 "Ignition System" in the 1990 "Y" Carline Service Manual has been revised as shown in the attached Figure 1. Please make a note of these changes for future reference.
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.
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