I believe it is because a DTC (error code) is in memory as a current code.
Try this. It really is for a 2001 but may work on your 2003.
Steps:
Disarm alarm if so equipped.
Run/Off switch to OFF
Ignition Key: ON,OFF,ON,OFF,ON (and leave ON)
Press LEFT turn signal switch TWICE. Wait for 1 or 2 flashes..
Press RIGHT turn signal switch ONCE => turn signal will flash 1 time
Press RIGHT turn signal switch ONCE => turn signal flashes 2 times
Press RIGHT turn Signal switch ONCE => turn signals flash 3 times
Press LEFT turn signal switch ONCE. TROUBLE CODES WILL NOW BE DISPLAYED (stream)
TO CLEAR ANY CODES,,,=> PRESS & HOLD LEFT signal switch for 5 seconds. => turn
signal will now flash twice to confirm memory is clear.
Turn ignition OFF.
See what happens!