GMC 1994 Yukon Owner's Manual page 338

Engine Emissions Classification
-
Gas Engines
Engine
Type
VIN
Fuel System
Emissions
'"Light Duty Emissions with 8500 GVWR and below or:
*"Heavy Duty Emissions with 8501 GVWR and above
+Throttle Body Injection
Engine Emissions Classification
-
Diesel Engines
Engine
Type
VIN
Fuel System
Emissions
6.5L
V8
S
Turbo Diesel
LD
6.5L
V8
F
Turbo Diesel
HD
7-4