DTC C1266: LR Outlet Valve Solenoid Malfunction: Notes
WARNING: This page is about a different car, the 1999 Buick Regal and 1999 Buick Century. However, it is still accessible from the selected car via links, so may be relevant.
NOTE:
The solenoid valve circuit and the solenoid coil are internal to the ECBM/EBTCM. No part of the solenoid circuit is diagnosable external to the ECBM/EBTCM. The DTC sets when there is a malfunction in the solenoid circuit internal to the ECBM/EBTCM only.