Great timing for me on this, as my 03 @ 150,000 had been throwing the glow plug code the past couple months. This letter came in the mail today.

"This letter is to inform you that some 2003 Chevrolet Silverado vehicles, equipped with a 6.6L diesel V8 engine, and California emissions or Clean Fuel Fleet emissions, may experience a condition where the engine glow plugs may fail. this will cause illumination of the Malfunction Indicator Light (MIL). ......"

General Motors is providing owners with additional protection for the engine glow plugs. If this condition occurs on your 2003 Chevrolet Silverado ... (LB7) and CA or Clean Fleet emissions, within 10 years or 200,000 miles,... the condition will be repaired for you at no charge. (Reimbursement also available for those who have paid for this repair.)

This is good news for those of us with 03 Ca emissions.