The 2020 Mercedes-Benz GLE W167 introduced the redesigned luxury SUV with the M256 3.0-liter turbocharged inline-6 engine in GLE 450 models. A P0305 diagnostic trouble code indicates the engine management system has detected misfire events specifically at cylinder 5 of this six-cylinder powerplant.
P0305 Code on Inline-6 Configuration
The P0305 code indicates "Cylinder 5 Misfire Detected." On the M256 inline-6 engine, cylinder 5 is legitimately the fifth cylinder in the sequential 1-6 numbering from front to rear. This cylinder fires second in the 1-5-3-6-2-4 firing order and its proper operation is essential for smooth engine performance.
Diagnosing Cylinder 5 Misfire Causes
On the 2020 GLE's M256 engine, cylinder 5 misfires commonly result from ignition coil failure losing spark energy, spark plug degradation affecting combustion efficiency, fuel injector malfunction causing improper fuel delivery, intake valve carbon deposits from direct injection operation, or mechanical issues such as valve sealing problems.
M256 Technology Overview
The M256 engine features an integrated starter-generator (ISG) on the 48-volt system, enabling EQ Boost assistance and efficient stop-start operation. The electric auxiliary compressor eliminates turbo lag. While this technology enhances performance, traditional ignition and fuel delivery systems remain primary misfire causes.
Repair Approach
Cylinder 5 misfire repair depends on identifying the specific failed component through systematic testing. Most repairs involve ignition components, fuel injectors, or in some cases, intake valve cleaning to remove carbon deposits that accumulate on direct-injection engines over time.