OBD-II code P0272 indicates the powertrain control module (PCM) has detected that cylinder 4 is not contributing its expected share of power to the engine, causing a balance or contribution fault. The PCM monitors crankshaft deceleration between power strokes and has flagged cylinder 4 as the source of an abnormal deviation. This is closely related to a cylinder 4 misfire but is reported by the contribution/balance monitor rather than the dedicated misfire counter.
An injector that is stuck open, stuck closed, or partially clogged is one of the most common causes of a contribution fault on a single cylinder because it directly changes how much fuel that cylinder receives.
A weak or failed ignition coil, worn spark plug, or damaged plug wire on cylinder 4 will prevent proper combustion and reduce that cylinder's contribution to engine output.
Mechanical issues such as a burned exhaust valve, worn piston rings, a leaking head gasket, or a damaged camshaft lobe can reduce compression in cylinder 4 and trigger the code.
An intake manifold leak, cracked hose, or failing intake gasket near cylinder 4 can lean that cylinder out and reduce its contribution to engine balance.
Corroded, loose, or chafed wiring to the cylinder 4 fuel injector or ignition coil can intermittently cut off that cylinder's fuel or spark.
A failing PCM is an uncommon cause of P0272 and should only be considered after all other possibilities have been ruled out through testing.
Short trips to a repair facility are usually fine, but the underlying problem can damage the catalytic converter over time and reduce drivability, so diagnosis should not be delayed for long.
In real-world cases the fix is almost always a fuel injector, ignition coil, spark plug, or repair of a vacuum or compression problem on cylinder 4, not a computer.
Clearing the code only resets the light temporarily; if the underlying mechanical, fuel, or ignition problem is not repaired, the code will return once the PCM's monitor runs again.
No. P0272 is very rarely caused by the engine computer, and drivers are sometimes steered toward a PCM replacement when the actual cause is a fuel injector, ignition component, vacuum leak, or compression issue. The PCM should only be suspected after every other possible cause has been tested and ruled out.