P2336

P2336 is a generic OBD-II code meaning the knock sensor detected cylinder 1 knock activity above the calibration threshold — the PCM monitors the piezoelectric knock sensor (0-5V signal range, AC waveform centered around a 2.5V bias) and band-pass filters it for the knock frequency band specific to the engine's bore (typically 5-15 kHz). When the filtered signal amplitude exceeds threshold during cylinder 1's combustion window, the PCM accumulates a knock count and, if the rate of events crosses calibration, sets P2336. This is a real knock event, not a sensor circuit fault (P0327/P0332 are sensor circuit codes). Cheapest-first ladder: (1) Pull live data and verify the knock-retard PID — if the PCM has pulled 4-8 degrees of timing from cylinder 1 specifically, the knock is real and current. Check fuel grade first: a customer who switched from 91 to 87 octane on a tuned or premium-required engine will throw P2336 within a tank ($0 fix, swap fuel). (2) Inspect for lean conditions on cylinder 1 — a clogged or dribbling injector, a vacuum leak at the cylinder 1 intake runner, or low fuel pressure all cause cylinder-1-specific lean burn that knocks. Smoke-test the intake. (3) Pull the spark plug on cylinder 1 and read it for pre-ignition signs (melted electrode tip, aluminum splatter, ceramic crack) — pre-ignition means heat soak or carbon glow plug effect, often from carbon buildup on the piston crown of direct-injection engines. (4) Pull the knock sensor and verify torque spec — knock sensors are torque-critical (typically 15-20 ft-lb on most platforms); over-torqued or under-torqued sensors produce false amplitude readings that look like real knock to the PCM. (5) Verify EGR isn't stuck closed on EGR-equipped engines — loss of EGR raises cylinder temps and induces knock under load. Expensive-misdiagnosis caveat: don't tear into the engine for piston/ring inspection on a P2336 without first ruling out carbon buildup on direct-injection intake valves — a walnut-blast service on a 2010+ DI engine ($300-450) often clears chronic cylinder-1 knock that mimics mechanical damage, because carbon flakes acting as hot-spots are the actual cause.

Vehicle-specific patterns: any direct-injection or turbocharged engine is P2336-prone — Ford EcoBoost 2.0/2.3/3.5L throws P2336 from carbon-fouled intake valves (no port-injection wash), from low-octane fuel on tuned vehicles, and from the well-known LPFP/HPFP fuel-pressure dropouts under boost. GM LSx and LT-series V8 (5.3L/6.0L/6.2L) sees P2336 from AFM/DFM lifter collapse on the deactivated cylinders, from carbon-induced pre-ignition on DI variants (LT1/LT4), and from worn knock-sensor harnesses under the intake. VW/Audi 2.0T TSI (EA888) throws P2336 from carbon buildup and from the well-documented HPFP cam-follower wear that drops fuel pressure under load. Subaru EJ25/FA20 sees P2336 from rod-bearing pre-failure (P2336 + tick at idle is the warning shot). Hyundai/Kia Theta II 2.0T and Lambda 3.3T GDI throw P2336 from carbon and from the recall-related rod-bearing failures that prompted the GDI engine warranty extensions. Estimated repair: $0 (fuel grade) to $4,500+ (engine internal).