Fuel Evap Canister vent solenoid failure symptoms, Diagnosis and resolution in detail. P0449 diagnostic trouble code resolution.
P0455 DTC means the hard line between the solenoid and charcoal canister may be cracked, and this video shows how to remove the solenoid and this hard line, so you can inspect and repair it.
Note that this code can be read with a low-cost engine diagnostic and scan tool. The code will clear by itself once the vehicle sees that the solenoid functions properly.
This video applies directly to GM suburban type of vehicles in late 2000, and specifically- the 2007 Cadillac Escalade was repaired in this video. The principles are applicable to any evap vent valve solenoid.
See how to test the solenoid, as it may not be dead, just full of dirt (dust) from the vent line.
See how to understand the wiring back to the solenoid, and test it for proper operation, with simple multi-meter that supports reading voltage and resistance (ohms).
See how to troubleshoot a broken wire from the Power Train Control Module (PCM) or Engine Control Module (ECM)- whichever you want to name it, using simple multi-meter on the Ohms setting.
See where the fuse is located that powers the solenoid.