SERVICE MANUAL UPDATE RWAL DIAGNOSTIC INFORMATION

Model and Year: 1988-90 C/K AND 1989-90 S/T/M AND 1990 R/V AND G TRUCKS

The attached chart (see Figure 1) is a revised code 5 diagnostic chart. The revised chart requires a check of wiring and the transfer case switch operation before the control valve is replaced on 4-wheel drive vehicles. The chart also revises code 5 diagnostic information in the following service manuals:

1988 C/K 1989 C/K 1990 C/K 1990 R/V AND G 1989 S/T 1990 S/T 1989 M VAN 1990 M VAN

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.