P0281
Cylinder 7 Contribution/Balance.
- Generic
- Powertrain
- Generic code
- Medium severity
How this code is built
- P
- SystemPowertrain
- 0
- Defined bySAE, the same on every car
- 2
- AreaFuel and air metering (injector circuit)
- 81
- FaultThe specific fault in that area
What it means
P0281 is the generic code for a cylinder 7 contribution or balance fault. The engine control unit monitors how much each cylinder contributes to engine speed, using crankshaft speed variation or similar methods. It has seen cylinder 7 contributing noticeably less (or more) than the others, so it has set the code. The exact test method and the cylinder numbering vary by manufacturer and engine.
Symptoms
- Rough running or a noticeable engine shake, especially at idle
- Misfire on one cylinder, possibly with the engine management light on or flashing
- Loss of power or hesitant acceleration
- Uneven or lumpy idle
- Increased fuel consumption
- Possible fuel smell or black smoke from the exhaust
Possible causes
- Faulty fuel injector on cylinder 7 (blocked, leaking, sticking or electrical fault)likely
- Worn or faulty spark plug or ignition coil on cylinder 7 (petrol engines)likely
- Wiring or connector fault to the cylinder 7 injector or coil, such as chafing, corrosion or a poor pin fitpossible
- Low compression on cylinder 7 due to valve, piston ring or head gasket problemspossible
- Vacuum or intake leak affecting cylinder 7, such as a split intake manifold seal or gasketpossible
- Crankshaft position sensor or reluctor wheel fault causing false balance readingsrare
- Fault within the engine control unit's driver circuit for that cylinderrare
How to diagnose
- Read all stored and pending codes and freeze frame data, noting engine load, speed and temperature when the fault set, and check for related misfire or injector codes
- Confirm the engine actually has a cylinder 7 and how cylinders are numbered for that model, as this depends on the engine layout
- Inspect the wiring and connectors to the cylinder 7 injector and coil for damage, corrosion, oil contamination or looseness
- Check live data for misfire counts and cylinder balance or contribution values to confirm cylinder 7 is the one at fault
- Swap the coil or injector from cylinder 7 with another cylinder, if the engine design allows, and see whether the fault follows the part
- Remove and inspect the spark plug on cylinder 7 for wear, fouling or damage (petrol engines)
- Carry out an injector electrical and flow or leak-off test, following the manufacturer's procedure for that engine
- Perform a compression or leak-down test on cylinder 7, and smoke test the intake for leaks
How to fix
- Replace or professionally clean or recondition the faulty injector on cylinder 7, as the manufacturer allows
- Replace the worn spark plug or failed ignition coil on cylinder 7, usually fitting a full set of plugs if they are due
- Repair or replace damaged wiring and clean or replace faulty connectors
- Rectify mechanical faults found by the compression test, such as valve, ring or head gasket repairs
- Replace leaking intake gaskets or seals
- Replace a faulty crankshaft sensor if testing shows it gives unreliable signals
Can I keep driving?
Short, gentle journeys to a workshop are usually acceptable, but the fault should be fixed soon. Avoid heavy loads, and stop driving if the engine management light flashes or the engine runs very roughly, as unburnt fuel can damage the catalytic converter and a mechanical fault could worsen.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.