Ignition fault on cylinder 2 (worn spark plug, failing coil or poor coil connection) causing inconsistent combustion; Cylinder 2 injector fault (partly blocked, leaking or sticking), giving uneven fuelling; Intake air leak, or carbon build-up on the inlet valves or ports near cylinder 2; Mechanical compression loss on cylinder 2 (burnt or sticking valve, worn piston rings, head gasket leak); Faulty cylinder pressure sensor, or damaged wiring or connector, on engines fitted with one; Outdated or faulty engine control unit calibration, where the manufacturer has identified it as a known cause.

P03A7

Cylinder 2 Pressure Variation High.

Generic
Powertrain
Generic code
Medium severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
3: AreaIgnition system or misfire
A7: FaultThe specific fault in that area

What it means

P03A7 means the engine control unit has detected that combustion pressure in cylinder 2 is varying more than expected from one cycle to the next, or from the other cylinders. How it is measured depends on the engine: some use an in-cylinder pressure sensor, others infer it from crankshaft speed or ion-current signals. The unit saw the cylinder 2 variation exceed its calibrated limit and set the fault.

Symptoms

Rough or uneven idle
Hesitation or jerking under load
Engine management light on, possibly flashing if a misfire is also present
Reduced power or the car going into limp mode
Poor fuel economy
Hard starting or a slight shudder when pulling away

Possible causes

Ignition fault on cylinder 2 (worn spark plug, failing coil or poor coil connection) causing inconsistent combustionlikely
Cylinder 2 injector fault (partly blocked, leaking or sticking), giving uneven fuellinglikely
Intake air leak, or carbon build-up on the inlet valves or ports near cylinder 2possible
Mechanical compression loss on cylinder 2 (burnt or sticking valve, worn piston rings, head gasket leak)possible
Faulty cylinder pressure sensor, or damaged wiring or connector, on engines fitted with onepossible
Outdated or faulty engine control unit calibration, where the manufacturer has identified it as a known causerare

How to diagnose

Read all stored and pending codes and the freeze frame data, noting load, engine speed and temperature when the code set. Look for related misfire, injector or ignition codes.
Check live data for cylinder 2 misfire counters, fuel trims and any cylinder pressure or rough-running values compared with the other cylinders.
Inspect the wiring, connectors and earths for the cylinder 2 coil, injector and (if fitted) pressure sensor for damage, corrosion or oil contamination.
Remove and inspect the cylinder 2 spark plug and compare it with the others. Swap the coil with another cylinder and see whether the fault follows it.
Check for intake leaks and vacuum leaks, for example with a smoke test, and inspect the inlet tract for contamination.
Test the cylinder 2 injector operation and balance or flow against the others, following the procedure for that engine.
Carry out a compression or leak-down test on cylinder 2 if the electrical and fuel checks are clear.
Check for any manufacturer software updates or technical bulletins for the engine concerned, as the procedure varies by model.

How to fix

Replace the cylinder 2 spark plug (preferably the full set) and any failed ignition coil.
Clean or replace the cylinder 2 injector if it is faulty.
Repair damaged wiring or connectors, or replace a faulty cylinder pressure sensor where fitted.
Repair intake leaks and clean carbon deposits using the method specified for that engine.
Carry out the necessary engine repair if compression is low, such as valve, piston ring or head gasket work.
Update the engine control unit calibration only if an outdated one is a documented cause for this engine.

Can I keep driving?

Medium severity

Short, gentle journeys are usually possible, but get it checked soon. If the warning light flashes, the engine runs very roughly or power drops sharply, stop driving, as unburnt fuel can damage the catalytic converter and a mechanical fault may worsen.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.