FALSE 'SERVICE ENG. SOON' REVISED CALIBRATION PROM CHART. GMC Truck GMC R Truck

VEHICLES AFFECTED: 1989 C/K/R/V AND G MODELS W/5.0 AND 5.7

Some 1989 C/K, R/V, & G model trucks with TBI engines may experience a False "Service Engine Soon " Light. If Code 32 EGR Diagnostic) or Code 45 (02 Sensor Rich) cannot be repaired using normal service procedures, a revised calibration PROM should be installed (See attached chart).

IMPORTANT: These new PROMS are for light duty emissions vehicles only (UNDER 8500 LBS. GVW).

NEW NEW B/CAST PROM CODE I.D. BODY EMISS. NEW PROM (PROM SCAN STYLE TYPE TRANS AXLE KIT LABEL) TOOL ----- ---- ----- ---- --- ----- ---- 5.0L ENGINE (RPO L03) ----------------------- NA5/NA6 M40 C,G,K1-2 FED/ALT SPD AUTO ALL 16139482 ASDK 9371

NA5/NA6 MD8 C1 FED/ALT 4 SPD AUTO GU2 2.73 16139487 ASDL 9381

NA5/NA6 MD8 GU4 3.08 c! FED/ALT 4 SPD AUTO GU6 3.42 16139492 ASDM 9391

G,K1 NA5/NA6 MD8 C,G,K2 FED/ALT 4 SPD AUTO ALL 16139492 ASDM 9391

NA5/NA6 MG5 C,K1-2 FED/ALT 5 SPD MAN ALL 16139497 ASDN 9401

NA5/NA6 MY6 G1-2 FED/ALT 4 SPD MAN ALL 16139502 ASDP 9411

5.7L ENGINE (RPO L05) --------------------- NA5/NA6 MD8 C,R,V1 FED/ALT 4 SPD AUTO GU2 2.73 16139558 ASDT 9451

NA5/NA6 MD8 GU4 3.08 C,R,V1 FED/ALT 4 SPD AUTO GU6 3.42 16139566 ASDU 9461 GT4 3.73

NA5/NA6 MD8 GU6 3.42 K1,C,K2 FED/ALT 4 SPD AUTO GT4 3.73 16139566 ASDU 9461 GT5 4.10

NA5/NA6 MD8 G1,2,3 FED/ALT 4 SPD AUTO ALL 16139566 ASDU 9461

G,K,V1 NA5/NA6 M20 G,K2 FED/ALT 4 SPD MAN ALL 16139544 ASDW 9471

NA5/NA6 MG5 C,K1,2 FED/ALT 5 SPD MAN ALL 16140637 ASDX 9481

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.