CLARIFICATION AND REVISION OF DIAGNOSTIC ROUTINE,C/C SYSTEM

VEHICLES AFFECTED: All 1985 Models Equipped With Cruise Control

Following is an explanation of both the present and revised diagnostic routines.

Present Diagnostic Sequence:

The existing diagnostic test procedure (see Figure 1) listed on the reverse side of the 'Quick Checker' includes five troubleshooting steps. Each step provides a reliable indication--by the illumination of a light--of the electrical continuity of specific components in the cruise control system. A large number of GM Dealership service personnel are under the misunderstanding that these same five steps, also, verify the condition of the cruise vacuum system. This is not the case. To clear up this mistaken assumption, an essential addition has been incorporated in the existing test procedure:

Revised Diagnostic Sequence:

Besides the listed 5 steps, a sixth one (see Figure 2) has been added. This step allows the technician to check the cruise system vacuum integrity from the accumulator tank through the vacuum servo.

The new diagnostic sticker can be obtained by ordering Part Number J34185L through General Motors of Canada Parts Department. Place the sticker over the one presently on the 'Quick Checker'.

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.