When your 2018 Chevrolet Silverado displays the P0305 code, the engine control module has detected repeated misfires in cylinder 5. The 2018 Silverado (final year of the third generation K2XX) offers the 4.3L V6, 5.3L V8, and 6.2L V8 engines—all of which have cylinder 5 and can legitimately trigger this code.
2018 Silverado Engine Options
The 2018 Silverado 1500 offered three gasoline engines: the 4.3L EcoTec3 V6 (285 hp), 5.3L EcoTec3 V8 (355 hp), and 6.2L EcoTec3 V8 (420 hp). All three engines use Active Fuel Management (AFM) cylinder deactivation technology.
Cylinder 5 Location
GM's cylinder numbering places odd numbers on the driver side. On V8 engines, cylinder 5 is at the front of the left bank. On the V6, cylinder 5 is in the center of the left bank. Access requires removing engine covers to reach the ignition coil and spark plug.
Common Causes at 2018 Mileage
A 2018 Silverado may have accumulated significant miles. AFM lifter failures are a known issue—the DOD (Displacement on Demand) solenoid and lifters can fail, causing misfires in specific cylinders. Spark plug wear is likely if original plugs haven't been replaced. Ignition coil degradation occurs over time. Oil quality and change intervals directly affect AFM lifter longevity.
Diagnostic Approach
Read all codes and check for AFM-related codes alongside P0305. Inspect spark plugs—GM recommends replacement at 100,000 miles but earlier may be beneficial. Test ignition coil operation. Check oil level and quality. If AFM lifter failure is suspected, a compression test and valve train inspection may be needed.