P2336 High Generic / SAE

P2336: Cylinder 1 Above Knock/Combustion Vibration Sensor Threshold

Powertrain Ignition, EGR and Glow Plug Control Emissions related

What to do

Avoid heavy acceleration, towing and long climbs until this is looked at — knock damages pistons and head gaskets, and it does so under load. The engine will feel flat and use more fuel, because the module is protecting itself by retarding the ignition timing; that flatness is the symptom, and you may hear nothing at all. If you can hear a sharp metallic rattle under acceleration, the protection has been exceeded — ease off and get it seen promptly. Before anything else, check what grade of fuel the manufacturer specifies and fill with it: that is free and it resolves a good share of these.

What this code means

Cylinder 1 is needing more knock protection than the module considers normal.

The first thing to be clear about is what this code does not say. It does not say the engine is detonating. The module manages knock continuously and successfully; this code fires when the amount of correction one specific cylinder requires has drifted beyond what the others need. It is a report about a margin being eaten, not about damage happening.

What knock actually is. Normal combustion starts at the spark plug and burns smoothly outward. Knock is the rest of the mixture igniting spontaneously ahead of that flame front, from heat and pressure alone, so two flame fronts collide. The resulting pressure spike is what makes the sharp metallic rattle under load — and it hammers the piston crown, the ring lands and the head gasket. Sustained knock is one of the few things that can destroy an engine quickly, which is why so much of the control strategy exists to prevent it.

How the module prevents it. A knock sensor is a piezoelectric microphone bolted to the block, listening for the characteristic frequency. When it hears knock, the module retards ignition timing until the knock stops. That works — at a cost in power and fuel economy, paid continuously and invisibly.

Which produces the most important practical consequence: the driver usually hears nothing. The symptom of a knock-prone cylinder is a flat, thirsty engine, not a noise. The noise only appears when the correction available has been exhausted. So if you can hear it, the protection has already been exceeded, and that is the point to stop pressing on.

Why a per-cylinder code is a diagnostic gift. Everything that causes knock across the whole engine — fuel quality, coolant temperature, intake air temperature, a stuck EGR valve, base timing — affects every cylinder roughly equally. A code naming one cylinder is therefore pointing at something that is true of that cylinder and not its neighbours, which is a much smaller list:

Carbon deposits raising the effective compression ratio in that cylinder.
A lean mixture on that cylinder, usually a partially blocked injector, because lean burns hotter.
A cooling problem local to it — a blocked passage, a failed gasket.
The wrong spark plug, or a worn one, or one of the wrong heat range.

The cheapest test comes before any of that, and it is free: put the correct grade of fuel in. Covered at P2337.

Worth distinguishing from the knock sensor codes at P0325–P0334, which are about the sensor's circuit. Those say the module cannot hear properly. This one says it heard something specific and did not like it. The standard's fuller name for that sensor — knock/combustion vibration — is the one this title uses, and the older wording is explained at P0325.

Likely causes

Start here

Incorrect or low octane fuel · easy
Carbon deposits in the combustion chamber · moderate
Clogged fuel injectors · moderate

Less common

Worn or fouled spark plugs · easy
Incorrect spark plug gap or heat range · easy
Stuck EGR valve · moderate
Engine overheating · moderate

Symptoms

Components involved

Information, not instruction

CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.

Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.

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