Some 1988 Broughams equipped with California emission systems, option code NB2, may experience a "Service Engine Soon" light with a diagnostic code 53. Code 53 indicates an EGR system malfunction and should be diagnosed using the procedures in the 1989 Brougham Service Information Manual.
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.