SERVICE GUILD: USE OF IAC DRIVER TOOL INFORMATON

VEHICLES AFFECTED: 1987-90 'A,J,L,W,' WITH 2.8L AND 3.1L (VIN T,W)

This bulletin is to inform General Motors Dealer Technicians using the Idle Air Control (IAC) Driver Tool "Special Tool" Number (22M - Concept Technology) or (J 37027 - Kent Moore) on all 2.8L/3.1L MPFI engines that the Diagnostic Test Terminal must be grounded or Field Service Mode entered if a "Scan Tool" is used.

The grounding procedure is fully explained in the diagnostic charts for Service Manual Sections "6E3-A" (Code 35) and "6E3-C2" (Idle Air Control (IAC) Circuit). However, the grounding procedure must also be followed when using the tool for other uses such as: Idle (RPM) Control, Generator Diagnosis, A/C Recharging, etc.

The engine carlines involved are as follows:

1989-1990 "A, J, L, W" Carlines 1988 "J" Carline 1987-1988 "A, L, W" Mass Air Flow to Speed Density Updates 1987 "J" Mass Air Flow to Speed Density Updates

It should also be noted that whenever the IAC system is disconnected or a battery disconnect is made, the "Idle Learn Procedure" in Section "6E3-C2" of the Service Manual should be followed.

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.