RE: Resetting the Change Oil message
From my 2005 Silverado manual:
The Engine Oil Life System calculates when to change
your engine oil and filter based on vehicle use.
Anytime your oil is changed, reset the system so it can
calculate when the next oil change is required. If a
situation occurs where you change your oil prior to a
CHANGE ENGINE OIL message being turned on, reset
To reset the Engine Oil Life System, do the following:
1. Turn the ignition key to RUN with the engine off.
2. Fully press and release the accelerator pedal three
times within five seconds.
If the OIL LIFE RESET message flashes for
10 seconds, the system is resetting.
3. Turn the key to LOCK.
If the CHANGE ENGINE OIL message comes back on
when you start your vehicle, the engine oil life system
has not reset. Repeat the procedure. If it still does
not reset, see your dealer for service.
Hope this works for your 03
Randy, Las Vegas