Get a scan done to see if any trouble codes are present system. Scan tool must be able to retrieve B codes, meaning code for Body Control Modules. If any trouble codes are present, it would help in the diagnostics of the problem.
Attached are the schematic for the headlights.
When problem occurs, unplug the high beam relay and test terminal 85 for continuity to ground. If continuity is found, the BCM is activating the relay.
Images (Click to enlarge)
Tuesday, January 11th, 2011 AT 4:32 PM