2010 Chevrolet Avalanche Owner's Manual - Page 408

To determine if the electrical fault is on the vehicle side or trailer side of the trailer wiring harness connection, do the following: 1. Disconnect the trailer wiring harness from the vehicle. 2. Turn the ignition OFF. 3. Wait ten seconds, then turn the ignition back to RUN. 4. If the CHECK TRAILER WIRING message re-appears, the electrical fault is on the vehicle side. If the CHECK TRAILER WIRING message only re-appears when connecting the trailer wiring harness to the vehicle, the electrical fault is on the trailer side. SERVICE TRAILER BRAKE SYSTEM - This message will be displayed when there is a problem with the ITBC system. If this message persists over multiple ignition cycles there is problem with the ITBC system. Take the vehicle to an authorized GM dealer to have the ITBC system diagnosed and repaired. If either the CHECK TRAILER WIRING or SERVICE TRAILER BRAKE SYSTEM message is displayed while driving the vehicle, power is no longer available to the trailer brakes. When traffic conditions allow, carefully pull the vehicle over to the side of the road and turn the ignition off. Check the wiring connection to the trailer and turn the ignition back on. If either of these messages continues, either the vehicle or trailer needs service. An authorized GM dealer may be able to diagnose and repair problems with the trailer. However, any diagnosis and repair of the trailer is not covered under the vehicle warranty. Please contact your trailer dealer for assistance with trailer repairs and trailer warranty information. 5-60