Chevrolet Venture 2003 Manual -

If gauges flicker, it is commonly a ground wire issue or a failing ignition switch, a known weak point in this generation.

11.3 quarts (10.7L) for standard cooling; 13.6 quarts (12.9L) with rear heating. Use DEX-COOL (orange). Chevrolet Venture 2003 Manual

If the automatic door fails, check the "On/Off" switch on the overhead console. Often, cleaning the brass contact pins on the door frame with rubbing alcohol restores the connection. If gauges flicker, it is commonly a ground

You can access the full, original factory owner's manual through several reliable digital sources: If gauges flicker