For 1990-2009 cars

# HEI MODULE TESTING CORRECT GROUNDING PROCEDURE

Known good HEI modules and new modules from service stock may fail a test using the HEI tester, J-24642, if the tester ground is improperly connected. When using the tester, connect or contact the alligator clip for the tester ground directly to the flat metal surface on the bottom of the HEI module (refer to Figure 1). The metal eyelet on the module is not always in contact with the metal ground surface on the bottom of the module and, therefore, should not be used when testing the module.

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.