The 2021 Chevrolet Express with the 6.6L V8 can experience AFM (Active Fuel Management) lifter failures, causing ticking noise and misfires. This common issue affects many GM V8 vehicles.
AFM System Overview
Active Fuel Management deactivates cylinders during light loads to improve fuel economy. Special collapsible lifters allow valve deactivation. These complex lifters have higher failure rates than conventional designs.
Symptoms of AFM Lifter Failure
Persistent Ticking
A failed lifter produces consistent ticking that doesn't improve with engine warm-up. The noise may be loudest on the affected bank.
Misfire Codes
A collapsed lifter prevents valve operation, causing misfires on the affected cylinder. P030X codes identify specific cylinders.
Rough Running
The cylinder with the failed lifter can't contribute power, causing rough running and vibration.
Loss of Power
With one or more cylinders not contributing, noticeable power loss occurs, especially under load.
Repair Options
Options include replacing only failed lifters, replacing all lifters, or converting to non-AFM lifters with an AFM delete kit.