2003 GMC Sonoma Owner's Manual - Page 384

99,000 Miles (165 000 km) 0 Change engine oil and filter (or every 3 months, whichever occurs first). An Emission Control Service. 0 Lubricate chassis components (or every 3 months, whichever occurs first). (See footnote #.) 0 Check rearlfront axle fluid level and add fluid as needed. Check constant velocity joints and axle seals for leaking. (See footnote **.) 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 onpage 5-27 for what to use. Inspect hoses. Clean radiator, condenser, pressure cap and neck. Pressure test cooling system and pressure cap. An Emission Control Service. 0 Inspect engine accessory drive belt. An Emission Control Service. 100,000 Miles (166 000 km) 0 Inspect spark plug wires. An Emission Control Service. 0 Replace spark plugs. An Emission Control 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. Long Trip/Highway Scheduled Maintenance The services shown in this schedule up to 100,000 miles (166 000 km) should be repeated after 100,000 miles (166 000 km) at the same intervals for the life of this vehicle. The services shown at 150,000 miles (240 000 km) should be repeated at the same interval after 150,000 miles (240 000 km) for the life of this vehicle. See Part B: Owner Checks and Services on page 6-25 and Part C: Periodic Maintenance Inspections on page 6-30. Manual transmission fluid doesn't require change. 0 4.3L V6 Engine Only: Inspect Positive Crankcase Ventilation (PCV) valve. An Emission Control Service. 6-17