GMC Sierra 1999, Owner'S Manual

Page: 392 / 432

Scheduled Maintenance
--
Gasoline Engines
yellow blue
7-16
100,000 Miles (166 000 km) (Continued)
j Change automatic transmission fluid and filter if the vehicle is mainly driven
under one or more of these conditions:
– In heavy city traffic where the outside temperature regularly reaches 90
_F
(32
_C) or higher.
– In hilly or mountainous terrain.
– When doing frequent trailer towing.
– Uses such as found in taxi, police or delivery service.
j If you haven’t used your vehicle under severe service conditions listed
previously and, therefore, haven’t changed your automatic transmission fluid,
change both the fluid and filter.
j Inspect Positive Crankcase Ventilation (PCV) valve.
An Emission Control Service.