Cylinder 8 is the rearmost cylinder on V8 engines, typically on the driver's side. Rear cylinders run hotter because they are furthest from the radiator and coolant input. This thermal load makes cylinder 8 prone to pre-ignition. When the computer detects knock in cylinder 8, it retards the ignition timing. If the knocking continues, it sets this fault code to warn the driver.
Mechanic Glossary
8 Above Knock Threshold
A diagnostic code indicating that combustion knocking in cylinder 8 exceeds safe parameters.
Frequently Asked Questions
The engine computer detected pre-ignition knocking in cylinder 8 that exceeded the safe operating noise limit.
It sits at the back of the engine block where coolant flow is reduced, causing it to run hotter than front cylinders.
Clean the combustion chambers, use high-octane fuel, and inspect the cooling system to ensure the rear of the engine is cooling properly.