The "service 4 wheel drive" light is on because the TCCM (Transfer Case Control Module) has detected a problem with the system. The light will remain on until the problem is fixed. Your local auto parts store can read the code(s) in the TCCM. The code(s) will help determine what the problem is.
2004 trailblazer have over drive
The 2004 Lamborghini Gallardo has all wheel drive.
The 2004 Nissan Murano has front wheel drive.
The 2004 Audi S4 has all wheel drive.
The 2004 Buick Regal has front wheel drive.
The 2004 Acura NSX has rear wheel drive.
The 2004 Kia Sedona has front wheel drive.
The 2004 Toyota Camry has front wheel drive.
The 2004 Dodge Durango has rear wheel drive.
The 2004 Hyundai Sonata has front wheel drive.
The 2004 Chevrolet Suburban has rear wheel drive.
The 2004 Honda Accord has front wheel drive.