Cylinder Deactivation (Active Fuel Management) System Diagnosis

Cylinder Deactivation (Active Fuel Management) System Diagnosis

Important: Active Fuel Management System Diagnosis is applicable for RPO LC9/LY5/LMG/L76.


1. Measure the engine oil level. Fill, as required.
2. Using the scan tool, inspect for diagnostic codes within the engine control module (ECM). Refer to Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle). Repair, as required.
3. Verify proper engine oil pressure and operation of the active fuel management oil pressure relief valve. Refer to Oil Pressure Diagnosis and Testing (Oil Pressure Diagnosis and Testing).
4. Verify proper operation of the active fuel management system components. Refer to Cylinder Deactivation (Active Fuel Management) System Compression Test (Cylinder Deactivation (Active Fuel Management) System Compression Test).
5. Remove the valve lifter oil manifold. Refer to Valve Lifter Oil Manifold Replacement (Valve Lifter Oil Manifold Replacement).
6. Verify proper operation of the valve lifter oil manifold. Refer to Cylinder Deactivation (Active Fuel Management) Valve Lifter Oil Manifold Diagnosis and Testing (Cylinder Deactivation (Active Fuel Management) Valve Lifter Oil Manifold Diagnosis and Testing).
7. Replace the active fuel management valve lifters, as required. Both intake and exhaust lifters should be replaced in pairs. Refer to Valve Lifter Replacement (Without AFM) (Valve Lifter Replacement (Without AFM))Valve Lifter Replacement (With AFM) (Valve Lifter Replacement (With AFM)).