SERVICE MANUAL UPDATE-SEC.8A THEFT DETERRENT SYSTEM

VEHICLES AFFECTED: 1989-90 F, W/5.0, 5.7, 3.1

Application: 1989 F cars with the following engine

options: 5.0 LB9 V-8 Vin Code F 5.7 L98 V-8 Vin Code 8 5.0 L03 V-8 Vin Code E

1990 F cars with the following engine

options: 5.0 LB9 V-8 Vin Code F 5.7 L98 V-8 Vin Code 8 5.0 L03 V-8 Vin Code E 3.1 LHO V-8 Vin Code T

Overview of Pass Key Theft Deterrent System Diagnostic Codes 46/53:

The ECM will not pulse the injectors "On" and thus allow the vehicle to be started unless it receives the proper signal from the Pass Key decoder module. Failure oE the proper signal to reach the ECM may be reported as a Code 46 on some PFI engines or as a Code 53 on some TBI engines. Not all engines will set a code when the proper signal fails to reach the ECM.

Diagnostic Procedures:

The following table defines where codes 46 or 53 will or will not be set, and the proper procedures for diagnosis of the Pass Key Theft Deterrent System.

MODEL CODES DIAGNOSTIC ENGINE YEAR SET PROCEDURES

5.0L LB9 V-8 1989 NONE Use procedures in 5.7L L98 V-8 1989 NONE Product Service 3.IL LHO V-6 1990 NONE Bulletin #89-8-201

5.0L L03 V-8 1989 53 Use diagnostic 5.0L LB9 V-8 1990 46 procedures in 1991 5.7L L98 V-8 1990 46 F-Car Service Manuals 5.0L L03 V-8 1990 53

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.