The P0302 trouble code on your 2020 Chevrolet Suburban indicates that cylinder 2 is experiencing misfires detected by the powertrain control module. As the final year of the eleventh generation, the 2020 Suburban features the 5.3L EcoTec3 V8 (L83) or available 6.2L EcoTec3 V8 (L86), both equipped with Active Fuel Management (AFM) cylinder deactivation technology.
AFM Technology and Cylinder 2
Cylinder 2 on GM's V8 engines is located on the passenger side bank and is one of the cylinders that can be deactivated by the AFM system during light-load driving. The AFM lifters use oil pressure to collapse and hold valves closed, effectively shutting down the cylinder. When these lifters malfunction, they commonly cause cylinder-specific misfires.
Common Causes of Misfire
AFM lifter failure is the most frequently reported cause of cylinder 2 misfires on 2020 Suburban V8 engines. The collapsible lifter mechanism can wear, stick, or fail entirely. Other causes include ignition coil failure, spark plug wear or fouling, fuel injector problems, and carbon buildup from direct injection. Low oil pressure or contaminated oil can affect AFM operation.
Symptoms Beyond Check Engine Light
You may notice rough idle, particularly when AFM is active. Engine vibration through the steering wheel and seats is common. Hesitation during acceleration, reduced fuel economy, and a rhythmic misfire sound under the hood indicate cylinder 2 is not contributing power consistently.
Diagnostic Approach
Check for related TSBs on AFM lifter issues. Scan for all codes and monitor AFM activation status. Inspect spark plug and ignition coil on cylinder 2. Verify oil level, condition, and pressure. Use a stethoscope to listen for valve train noise indicating lifter problems. Compression testing confirms cylinder integrity.
Effective Repairs
Simple fixes include spark plug and coil replacement. If AFM lifter failure is confirmed, options include lifter replacement with updated GM parts or an AFM delete kit that replaces collapsible lifters with standard lifters and includes a tune to disable AFM. Regular oil changes with Dexos1 approved oil help prevent future AFM issues.