The P0302 trouble code on your 2018 GMC Sierra indicates cylinder 2 is misfiring. This generation Sierra features proven powertrains, but misfires require proper diagnosis to prevent costly secondary damage.
2018 Sierra Engine Options
The 2018 GMC Sierra 1500 came with three engine choices: the 4.3L V6, 5.3L V8, and 6.2L V8. The V8 engines feature Active Fuel Management (AFM) cylinder deactivation, which can contribute to misfire conditions.
AFM System Concerns
Active Fuel Management on the 5.3L and 6.2L V8 deactivates four cylinders during light-load driving. Cylinder 2 is one of the cylinders that can be deactivated. AFM lifter failure is a documented concern on these engines, often causing misfires, lifter tick, or collapsed lifters.
Carbon Buildup Consideration
At this age, direct injection-equipped engines may have significant carbon buildup on intake valves. This affects airflow into the cylinders and can cause misfires. Walnut shell blasting or chemical cleaning may be necessary.
Standard Ignition Diagnosis
Begin with fundamental ignition checks: spark plug condition, ignition coil function, and wiring integrity. The 2018 Sierra uses a coil-on-plug system where each cylinder has a dedicated ignition coil, simplifying diagnosis.
Fuel Injector Testing
Direct fuel injectors can develop issues over time. Restricted or leaking injectors affect cylinder 2's fuel delivery. Scan tool analysis of fuel trims and injector pulse width provides diagnostic insight.