The P0304 code in your 2018 Chevrolet Silverado indicates the engine management system has detected persistent misfires in cylinder 4. As the final year of the K2XX generation Silverado, the 2018 model uses Active Fuel Management (AFM) on V8 engines—a system with documented lifter concerns that warrant special attention during misfire diagnosis.
Understanding P0304 in the 2018 Silverado
The 2018 Silverado's 5.3L and 6.2L V8 engines feature Active Fuel Management, the predecessor to Dynamic Fuel Management found in newer models. AFM deactivates four cylinders under light load conditions using hydraulically-controlled switching lifters. Cylinder 4, positioned on the right bank, is one of the AFM-controlled cylinders. This system has experienced documented lifter failure patterns that can cause misfire codes.
AFM-Related Misfire Concerns
The AFM system's switching lifters have gained notoriety for failure, particularly in higher-mileage vehicles. Lifter collapse or sticking prevents proper valve operation, directly causing misfires. Warning signs include distinctive ticking noises, especially noticeable at cold start. Beyond AFM issues, standard causes including spark plug and ignition coil wear remain common on this mature platform with potentially significant accumulated mileage.
Diagnostic Protocol
Retrieve all codes and note any AFM-related faults or valve train codes accompanying P0304. Listen carefully for lifter noise at startup and idle. Given the 2018 model's age, inspect spark plug condition thoroughly—these are likely original if not previously replaced. Verify oil level and condition as AFM operation depends heavily on proper hydraulic pressure from quality oil.
Repair Options
Replace ignition components showing wear—spark plugs and coils should be tested and replaced as needed. AFM lifter failure typically requires cam-in-block lifter replacement, a major repair. Many owners choose to install AFM disabler devices that keep all cylinders firing, preventing further lifter cycling wear while maintaining driveability.