P2365 indicates that the engine control module has detected poor combustion performance specifically on cylinder 11. This is a cylinder-specific fault similar in nature to a misfire code, meaning that cylinder is not contributing normally compared to the others. The code applies primarily to engines with at least 11 cylinders, such as V12 configurations.
On cylinder 11 specifically, a worn spark plug or failed ignition coil is the most common cause of poor combustion performance. This should be the first component group evaluated.
A clogged, leaking, or electrically failed fuel injector can cause that cylinder to run lean, rich, or not fire at all. Injector balance testing helps isolate this.
A leaking intake manifold gasket or vacuum path near cylinder 11 can introduce unmetered air and disrupt combustion. This is more likely on engines with individual runner designs.
Loss of compression from worn piston rings, valves, or a leaking head gasket can cause poor combustion on one cylinder. A compression or leak-down test is needed to confirm.
Corroded, chafed, or loose wiring at the cylinder 11 ignition coil or fuel injector can interrupt operation. This is less common but should be verified before replacing parts.
A failed driver circuit inside the PCM for cylinder 11 is rare. It should only be considered after all ignition, fuel, mechanical, and wiring causes have been conclusively ruled out.
No. PCM/ECM failure is very rarely the cause of this code. The problem is almost always ignition, fuel, mechanical, or wiring related. Replacing the computer should be a last resort only after thorough testing.
Extended driving with a cylinder performance fault can damage the catalytic converter from unburned fuel and may cause rough running. It is best to diagnose and repair promptly.
This code only appears on engines with at least 11 cylinders, typically V12 engines. The vehicle's service manual will define which physical cylinder is number 11 for your engine layout.
If the cause is a worn spark plug or weak coil, replacing those parts on cylinder 11 will resolve it. However, the code has multiple possible causes, so proper diagnosis is needed rather than guessing.