Go to the backing plate and get a short pry bar or really big, fat screwdriver and move the lever with the cable on it towards the front. You should be able to visually see it moving pretty much all the way back on its own when you let go.
Do it with a wheel off the ground, turn the wheel...and keep trying to turn it while it releases. Or, have a buddy apply the ebrake while you do that and make sure it's disengaging.
If it's sticking, you need to find out if it's the cable or the lever itself. If it's the cable, 90% of the time you gotta replace it...if it's the lever/mechanism, you'll have to take it all back apart more than likely and clean it really good with a wire brush/sandpaper and lube it really good with the same grease (hopefully high temp synthetic brake grease) that you lubed the 6 spots on each backing plate, and the metal to metal contact points where the ebrake lever contacts the back of the rear shoe.
02 Ext Cab | 4x4 | 3.0 | M50D-R1 | 3" PA BL | 33x12.50x15 Dynapro M/T's | 15x8 Soft 8's