Replace spark plugs and inspect fuel system.
If you prefer a hard copy, sites like eBay or Helm Inc. (the official GM literature provider) are your best bets. 2. Key Specifications & Fluid Capacities Chevrolet Venture 2003 Manual
The 2003 Venture has a few known quirks often mentioned in technical guides: Replace spark plugs and inspect fuel system
Flush and replace cooling system (DEX-COOL). 4. Common Troubleshooting "Quick Fixes" Chevrolet Venture 2003 Manual
If an electronic component stops working, check these two locations:
11.3 quarts (10.7L) for standard cooling; 13.6 quarts (12.9L) with rear heating. Use DEX-COOL (orange).