ALCL SCAN TOOL DIAGNOSIS PROM CHANGE/ PART #'S

VEHICLES AFFECTED: 1984 T-Type Rivieras and Regals

Early production Rivieras and Regals equipped with turbocharged 3.8L SFI engines may have PROM's that are not compatible with the updated or new ALDL (ALCL) scanner tools when operated in the open mode.

If you are servicing early production vehicles and are unable to obtain useful diagnostic information when using the ALDL (ALCL) scanner tool in the open mode it may be necessary to replace the prom.

VIN break points for open mode diagnostic proms are as follows:

MODEL VIN BREAK POINTS NEW PROM BROADCAST CODE ----- ---------------- -------- ------------- Riviera EE428568 16045886 DNP Regal EH525499 1226923 DNN

Information displayed in the open mode with this change is as follows:

Oxygen sensor voltage Air Flow Knock retard (in degrees) Block learn fuel Idle air control Engine RPM Part Neutral switch Torque converter clutch Power steering (FWD only) EGR (Turbo reads 3rd gear switch when in this position) 4th gear switch Air conditioning (on/off status)

NOTE: Vehicles with VIN's above those listed in this bulletin have the latest open mode diagnostic PROM installed and will not benefit from this change.

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.