When your 2023 Chevrolet Suburban displays the P0305 code, the engine control module has detected repeated misfires in cylinder 5. The 2023 Suburban offers V8 engines (5.3L and 6.2L) and the 3.0L Duramax inline-six diesel. All configurations have at least six cylinders, making P0305 a valid diagnostic code.
2023 Suburban Engine Options
The 2023 Suburban (twelfth generation) offers the 5.3L V8 (355 hp), 6.2L V8 (420 hp), and 3.0L Duramax I-6 diesel (277 hp). The V8 engines use Dynamic Fuel Management (DFM), while the diesel has a different architecture.
Cylinder 5 Location
On V8 engines, cylinder 5 is at the front of the driver side bank. On the inline-six diesel, cylinder 5 is toward the rear of the engine. GM's V8 cylinder numbering places odd cylinders on the driver side.
Common Causes
DFM lifter issues continue to be reported on some GM V8 engines, with lifter failures causing misfires in specific cylinders. Spark plug wear occurs over time, particularly with towing. Ignition coil failure is possible. Carbon buildup from direct injection affects valve sealing. Fuel system issues can cause lean misfires.
Diagnostic Approach
Identify your engine configuration. Read all codes including DFM-related codes on V8 models. Inspect cylinder 5's spark plug and ignition coil. Check oil condition—DFM requires clean, proper-viscosity oil. Review GM TSBs for known issues with the 2023 model year.