When your 2021 Chevrolet Tahoe displays the P0305 code, the engine control module has detected repeated misfires in cylinder 5. The 2021 Tahoe (first year of the fifth generation T1XX platform) offers V8 engines including the 5.3L V8 and 6.2L V8, as well as the 3.0L Duramax diesel inline-six. All configurations have at least six cylinders, making P0305 a valid diagnostic code.
2021 Tahoe Engine Options
The redesigned 2021 Tahoe offers the 5.3L V8 (355 hp), 6.2L V8 (420 hp), and 3.0L Duramax inline-six diesel (277 hp). The V8 engines use Dynamic Fuel Management (DFM) cylinder deactivation, while the diesel uses a different architecture.
Cylinder 5 Location
On GM's V8 engines, cylinder 5 is at the front of the driver side (left) bank. GM's firing order places odd-numbered cylinders on the driver side. Access requires removing the engine cover to reach the ignition coil and spark plug.
Common Causes
Dynamic Fuel Management (DFM) lifter issues have been documented on some GM V8 engines, potentially causing misfires in specific cylinders. Spark plug wear can occur, especially with towing or heavy use. Ignition coil failure is possible. Fuel injector issues or carbon buildup from direct injection can contribute.
Diagnostic Process
Read all codes including any DFM or lifter-related codes. Inspect cylinder 5's spark plug for wear or fouling. Test the ignition coil. Check oil level and quality—DFM systems require clean, proper-weight oil. If DFM lifter failure is suspected, valve train inspection and compression testing may be needed.