2003 GMC Sierra 1500 Pickup Owner's Manual - Page 509

100,000 Miles (166 000 km) 0 Inspect spark plug wires. An Emission Control Service. 0 Replace spark plugs. An Emission Control Service. 0 Change automatic transmission fluid and filter if the vehicle's GVWR is over 8600 Ibs, if the vehicle has an Allison transmission or 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. 0 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 0 Automatic Transfer Case Only: Change transfer case fluid 0 Except 8.1 L V8 Engine: inspect Positive Crankcase Ventilation (PCV) valve.An Emission Control Service. 150,000 Miles (240 000 km) 0 Drain, flush and refill cooling system (or every 60 months since last service, whichever occurs first). See Engine Coolant on page 5-33 for what to use. Inspect hoses. Clean radiator, condenser, pressure cap and neck. Pressure test the cooling system and pressure cap. An Emission Control Service. 0 Change five-speed manual transmission fluid (with 4300 V6 or 4800 V8 engines only). 0 Inspect engine accessory drive belt. An Emission Control Service. 200,000 Miles (332 000 km) 0 6000 V8 Engine Only: Change five-speed manual transmission fluid. 6-10