For 1990-2009 cars

# INOP O2 SENSOR, CODES 13,55,45 MUD AROUND BOOT

WHEN DIAGNOSING A CONDITION FOR AN INOPERATIVE OXYGEN SENSOR, PAY CLOSE ATTENTION TO THE CONDITION OF THE SENSOR BOOT. IF THE RUBBER BOOT BECOMES CAKED WITH MUD OR DIRT, IT MAY BECOME INOPERATIVE. SLIDING THE BOOT BACK AWAY FROM THE SENSOR AND CLEANING IT, MAY RESTORE THE OXYGEN SENSOR TO NORMAL OPERATION.

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.