Caution: Unless directed otherwise, the ignition and start switch must be in the OFF or LOCK position, and all electrical loads must be OFF before servicing any electrical component. Disconnect the negative battery cable to prevent an electrical spark should a tool or equipment come in contact with an exposed electrical terminal. Failure to follow these precautions may result in personal injury and/or damage to the vehicle or its components.

1. Remove the components as follows from the cylinder heads:

•	The gas mass sensor/mixture control valve (GMS/MCV) and bracket. Refer to Gas Mass Sensor/Mixture Control Valve and Mounting Bracket Replacement in Engine Controls - 5.0, 5.7L.

•	The low pressure regulator (LPR) and adapter. Refer to Compressed Natural Gas Low Pressure Regulator and Bracket Replacement in Engine Controls - 5.0, 5.7L.

•	The gas distribution adapter (GDA). Refer to Gas Distribution Adapter Replacement in Engine Controls - 5.0, 5.7L.

•	The union to low pressure lock-off (LPL) fuel line. Refer to Fuel Hoses/Lines Replacement - Intake Manifold to Low Pressure Lock-Off in Engine Controls - 5.0, 5.7L.

•	The high pressure regulator (HPR) to union fuel line. Refer to Fuel Hoses/Lines Replacement - High Pressure Regulator to Intake Manifold in Engine Controls - 5.0, 5.7L.

2. Remove the cylinder heads. Refer to Cylinder Head Replacement (Lower) in Engine Mechanical in the C/K Truck Service Manual.

1. Install the cylinder heads. Refer to Cylinder Head Replacement (Lower) in Engine Mechanical in the C/K Truck Service Manual.
2. Install the components as follows into the cylinder heads:

•	The gas mass sensor/mixture control valve (GMS/MCV) and bracket. Refer to Gas Mass Sensor/Mixture Control Valve and Mounting Bracket Replacement in Engine Controls - 5.0, 5.7L.

•	The low pressure regulator (LPR) and adapter. Refer to Compressed Natural Gas Low Pressure Regulator and Bracket Replacement in Engine Controls - 5.0, 5.7L.

•	The gas distribution adapter (GDA). Refer to Gas Distribution Adapter Replacement in Engine Controls - 5.0, 5.7L.

•	The union to low pressure lock-off (LPL) fuel line. Refer to Fuel Hoses/Lines Replacement - Intake Manifold to Low Pressure Lock-Off in Engine Controls - 5.0, 5.7L.

•	The high pressure regulator (HPR) to union fuel line. Refer to Fuel Hoses/Lines Replacement - High Pressure Regulator to Intake Manifold in Engine Controls - 5.0, 5.7L.