CORRECT USE OF J26792 (ST125) ALL VEH WITH ELECTRONIC DIS

SUBJECT: INFORMATION ON CORRECT USE OF J-26792 (ST-125)

MODELS AFFECTED: 1984-92 ALL MODELS WITH ELECTRONIC DISTRIBUTORLESS IGNITION (DIS) SYSTEMS

NOTICE: The following conditions may cause damage to ignition system components or incorrect diagnosis and replacement of good parts due to excessive secondary voltages required to fire the ST-125:

- Failure to ground secondary wire for companion cylinder. - Use of more than one ST-125 on a single coil. - Failure to clip ST-125 directly to ground.

When connecting the ST-125 HEI Spark Tester (J-26792) to vehicles equipped with Electronic Distributorless Ignition (DIS) Systems, the following procedure must be used to avoid damage to ignition system components and misdiagnosis:

1. Install ST-125 at plug end of secondary wire for suspect cylinder and clip ST-125 to ground at engine block. Avoid placing ST-125 near Sensors, Modules, or other Electronic Devices which may be affected by electromagnetic interference.

2. Disconnect plug end of secondary wire for companion cylinder and jumper directly to ground at engine block.

3. Continue with appropriate diagnosis. (Chart A-3, Chart C-4, or "Symptoms" Section "6E3-B").

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.