For 1990-2009 cars

# FALSE TROUBLE CODE 42 AFTER CYCLING IGNITION SWITCH

SOME OF THE ABOVE VEHICLES MAY EXPERIENCE FALSE TROUBLE CODE 42. THE FALSE CODE IS DETECTED IN TWO (2) WAYS -- EITHER A HARD CHECK ENGINE LIGHT AFTER AN IGNITION CHECK (IGNITION OFF AND BACK ON WITHIN FIVE (5) SECONDS), OR NO CHECK ENGINE LIGHT BUT MALFUNCTION CODE 42 STORED IN MEMORY. THE INCIDENTS ARE GENERATED ON VEHICLES INCORPORATING A "GENERATOR" LIGHT AND NO INCIDENTS WITH VOLTMETER. THIS CONDITION CAN BE ALLEVIATED BY CONNECTING P/N 12047479 (DIODE JUMPER ASSEMBLY) AS SHOWN IN ATTACHED GRAPHICS.

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.