Special Coverage. Certain vehicles equipped with a 6.6L diesel engine (RPO L5P), may have a condition that could cause the engine glow plugs to fail. If this condition occurs, the Malfunction Indicator Light (Check Engine Light) will illuminate and a diagnostic trouble code will set. Additionally, the engine may be hard to start or the engine may run rough immediately following engine start. Dealers are to replace the glow plugs as necessary. The repairs will be made at no charge to the customer.