GMC 1994 Yukon Owner's Manual page 346

GASOLINE ENGINES WITH HEAVY DUTY EMISSIONS
-
MAINTENANCE SCHEDULE / I f
*
An Emission Control Service
**
See "Explanation of Scheduled Maintenance Services" in the Index.
A
A Noise Emission Control Service
1 /
Applicable only to vehicles
sold
in the United States
t
To determine the emissions classification of your engine, refer to "Selecting the Proper
Maintenance Chart'' in this section.
TO406
7- 12