2004 Chevrolet Impala Owner's Manual - Page 206

TRAF (Traffic): If TRAF appears on the display, the tuned station broadcasts traffic announcements and when a traffic announcement comes on the tuned radio station you will hear it. If the current tuned station does not broadcast traffic announcements, press the TRAF button and the radio will seek to a station that does. When the radio finds a station that broadcasts traffic announcements, the radio will stop and TRAF will be displayed. When a traffic announcement comes on the tuned radio station you will hear it. If no station is found, NO TRAF will appear on the display. If TRAF is on the display you can press the TRAF button to turn of the traffic announcements. Your radio will play the traffic announcement even if the volume is muted. Your radio will interrupt the play of a cassette tape or a CD if the last tuned station broadcasts traffic announcements. This function does not apply to XM™ Satellite Radio Service. Radio Messages CAL ERR (Calibration Error): Your audio system has been calibrated for your vehicle from the factory. If CAL ERR appears on the display it means that the radio has not been configured properly for the vehicle and must be returned to the dealer for service. LOCKED: This message is displayed when the THEFTLOCK® system has locked up. You must return to the dealer for service. If any error occurs repeatedly or if an error cannot be corrected, contact your dealer. 3-84