Sponsored Links General Motors has issued a service update for certain examples of the Chevy Silverado HD and GMC Sierra HD pickup trucks equipped with the 6.6L L5P V8 Duramax diesel engine due to an issue related to the NOx sensor and engine control unit. The problem: in affected vehicles, the Malfunction Indicator Lamp (MIL) or ‘Service Engine Soon’ light may appear illuminated on the instrument panel. GM service technicians may also find a diagnostic trouble code (DTC) of P11D5 when trying to assess the problem with the vehicle. The hazards: this problem does not pose a safety risk to the driver or vehicle occupants. Most owners will not want to drive around with a MIL or Service Engine Soon light illuminated on the instrument panel, however.