Possible causes – Faulty Oxygen sensor– Ignition problem– Fuel injection problem– Engine mechanical condition Tech description There is a factory service bulletin for the following HUMMER models: 2003-2008 HUMMER H22003-2008 HUMMER Factory Service Bulletin OBDII Code P1174 Symptoms – Engine Light ON (or Service Engine Soon Warning Light) P1174 HUMMER OBD Code Description The Engine…