RETAINING MEMORIES IN ELECT. DEVICES WITH BAT. DISCONNECTED

SUBJECT: INFORMATION ABOUT RETAINING MEMORY IN AUTOMOTIVE ELECTRONIC DEVICES WITH BATTERY DISCONNECTED

VEHICLES AFFECTED: 1979-91 OLDS VEHICLES ONLY

When performing many repair procedures, we recommend disconnecting the battery negative cable from the battery. When this is done certain component memories, such as radio station, clock, and auto air conditioning presets, and ECM idle learn are lost. The loss of radio and clock memory is an irritation to owners and loss of idle learn on some engines requires a technician to spend time doing the idle learn procedure. To eliminate these losses of memory you can install devices, prior to disconnecting the battery, that provide just enough current to keep the memory alive.

Devices that plug into the vehicle cigarette lighter and are powered by 9 volt batteries are available from many sources. Two such examples are Snap-on* YA960 or Kent-Moore* KS295A. However, when using 9 volt devices it is possible for the vehicle's electrical system voltage to drop enough to cause memory loss if a door is opened and the courtesy lamp switches close. To avoid this problem, remove the fuse for the courtesy lamp circuit prior to disconnecting the vehicle's negative battery cable providing that no memory devices are powered from that fuse. Also use batteries in good condition.

There are also devices, such as Kent-moore* BT-9027 that plug into the vehicle cigarette lighter and provide a 12V supply of electrical current. These devices have an advantage over those mentioned previously and are preferred if the vehicle is equipped with a BCM. They supply enough electrical current to sustain memory even when the doors are opened and courtesy lights are energized.

ANY of the memory saving devices mentioned above can supply enough current to deploy an SIR air bag. Therefore, always reference the appropriate service manual procedure for the vehicle system you are servicing. If specifically directed by the service procedure for the component(s) you are servicing, disable and enable the SIR system as outlined in "Disabling the SIR System" and "Enabling the SIR System" in that section.

CAUTION:

When performing service on or around SIR wiring, follow the procedure listed in service manual Section 9J to temporarily disable the SIR system. Failure to follow procedures could result in possible air bag deployment, personal injury or otherwise unneeded SIR system repairs.

* We believe these sources and their equipment to be reliable. There may be additional manufacturers of such equipment. General Motors does not endorse, indicate any preference for or assume any responsibility for the products or equipment from these firms or for any such items which may be available from other sources.

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.