SERVICE MANUAL UPDATE-SEC.6E2 REVISED CODE 53 (VATS)

VEHICLES AFFECTED: 1989 "F" 5.0L (VIN E)

The Code 53 Vehicle Anti-Theft System (VATS) service diagnostics for the 1989 5.0L L03 (VIN E) "F" car have been revised.

Use the information in this bulletin in place of the Code 53 chart and facing page schematic found on pages 6E2-A-52 and 6E2-A-53 in the "Driveability and Emissions" Section "6E2" for the above mentioned vehicle.

VEHICLE ANTI-THEFT SYSTEM (VATS) CIRCUIT 5.0L (VIN E) "F" CARLINE (TBI)

Circuit Description:

The VATS system is designed to disable vehicle operation if the incorrect key or starting procedure is used. The VATS decoder module sends a signal to the ECM if the correct key is being used. If the proper signal does not reach the ECM on CKT 229, the ECM will not pulse the injectors "ON" and thus not allow the vehicle to be started.

Code 53 will set, if the proper signal is not being received on CKT 229 ECM when the ignition is turned "ON." Code 53 does not store in the ECM memory but is only present when the conditions stated above are met.

Test Description: Numbers below refer to circled numbers on the diagnostic chart.

1. If the engine cranks, and a Code 53 is stored, it indicates that the portion of the module which generates the signal to the ECM is not operating or CKT 229 is open or shorted to ground. If the decoder module is found to be OK, as determined from Section "8A", the ECM may be at fault, but this is not a likely condition.

2. If Code 53 is stored, and the engine will not crank, it indicates that there is a non-ECM related VATS problem or an incorrect key or starting procedure is being used.

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.