Cylinder 12 is the rearmost cylinder in a V12 engine block on the passenger side. Rear cylinders run hotter because they are furthest from the radiator. This thermal load makes cylinder 12 prone to pre-ignition. When the computer detects knock in cylinder 12, it retards the ignition timing. If the knocking continues, it sets this fault code to warn the driver.
Mechanic Glossary
12 Above Knock Threshold
A fault indicating that combustion vibrations in cylinder 12 of a V12 engine exceed safe parameters.
Frequently Asked Questions
It sits at the back of the engine block where coolant flow is reduced, causing it to run hotter than front cylinders.
The engine control unit detected pre-ignition knock in cylinder 12 that exceeded the safe operating noise limit.
Clean the combustion chambers, use high-octane fuel, and inspect the cooling system to ensure the rear of the engine is cooling properly.