Check Valve Test

To determine if the check valve has failed, remove the air hose from the valve inlet tube. Failure of the valve will be indicated by exhaust gas flow from the inlet tube. This valve is not serviceable, and must be replaced if defective.
If the exhaust manifold injection tube assembly is leaking, remove tube assembly and replace gasket material. If the tube nut joint is leaking, retorque to 30 ft lbs.