Go back to the dealer and get your $100 refunded. The glow plugs and controller do fall under the emission system warranty which is 100,000 miles. The dealer should not have used your extended warranty as the repair is covered by Chevrolet and there is no deductible.Just had the same code. Took it to the dealer and had if fixed under extended warranty. Service rep. advised that glow plugs fall under the 100,000 mile emissions warranty. Found that the glow plug controller was bad. 75,000 miles. Payed $100.00 deductable.