Place cod in cool water to thaw completely.
Pat fish dry with paper towels.
Mix olive oil with lemon juice and brush over both sides of fish.
Combine garlic, cumin, chili powder, salt and pepper. Sprinkle over fish.
Prepare a grill fire to about 300° with pecan or oak for smoke flavor.
Place fish over indirect fire, using a grill pan if needed. Cook with the lid closed for 10 minutes. Start checking the fish with a meat thermometer, cooking until it reaches 145° in the middle. Fish will be flaky when it's cooked through.
Remove from grill to a serving platter and flake to serve on tacos.
Cook corn tortillas on both sides for about 1- 2 minutes.
Mix fish taco sauce together by combining sour cream, mayonnaise, lime juice, cumin, garlic and salt. Can be made ahead and stored in refrigerator until serving.
Serve warmed tortillas with flaked fish, shredded cabbage, fish taco sauce, pico de gallo, avocado, onions and cilantro.