When your 2022 GMC Sierra displays the P0303 code, the powertrain control module has identified repeated misfires in cylinder 3. The 2022 Sierra features GM's T1 platform with advanced V8 engines using Dynamic Fuel Management technology.
Understanding the Sierra's V8 Engines
The 2022 Sierra offers the 5.3L L84 or 6.2L L87 V8 engines with DFM cylinder deactivation. Cylinder 3 is positioned on the driver's side (left bank). The DFM system can deactivate cylinder 3 during light load conditions, adding complexity to misfire diagnosis.
Primary Causes
- DFM Lifter Failure: Cylinder deactivation lifters are a known failure point
- Ignition Coil Degradation: Coil-on-plug units fail from heat and age
- Spark Plug Wear: GM V8s require specific iridium plugs
- Fuel Injector Issues: Direct injection deposits affect spray patterns
- AFM/DFM Solenoid Problems: Oil control solenoids affect lifter operation
Diagnostic Process
Use a GM-compatible diagnostic tool to monitor DFM operation and misfire counts. Check if misfires occur primarily during or after DFM activation. Test ignition system components. Research current TSBs addressing lifter concerns.
Recommended Repairs
Replace ignition coils with AC Delco parts if electrical failure confirmed. Install GM-specified spark plugs. For DFM-related misfires, lifter replacement following GM procedures is typically required. Consider AFM/DFM delete if lifters are replaced.