On 1991 "C" (Ninety-Eight) models equipped with the digital cluster (U2A), the "Oil Indicator" symbol will not light when the ignition switch is on and the engine is not running (bulb check mode).
This condition is due to software programming in the digital cluster assembly. Please do not attempt to repair this condition. Software programming will be changed to include the oil indicator bulb check feature at the start of Production for 1992.
With the engine running, the "Oil Indicator" symbol will light to alert the driver of any abnormal condition as will the Driver Information Centre information screen.
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.