P02A2

What it means

P02A2 means the engine control unit has had to push the individual fuel correction for cylinder 3 to its maximum limit, either adding or removing fuel, and still cannot get that cylinder's mixture right. It compares the cylinder's measured combustion or exhaust response with what it expects and keeps adjusting until it runs out of authority. The cause is usually local to cylinder 3, though how cylinder trim is measured depends on the engine.

Symptoms

• Engine management light on
• Rough idle or a noticeable misfire on one cylinder
• Hesitation or uneven power under load
• Poor fuel economy or a smell of fuel
• Hard starting or rough running when cold
• Possible additional misfire or fuel trim codes stored

Possible causes

• Cylinder 3 fuel injector partly blocked, leaking or stickinglikely
• Injector wiring or connector fault on cylinder 3 (high resistance, corrosion, damaged loom)possible
• Air leak near cylinder 3, such as a split intake hose, worn manifold gasket or leaking port seal, causing a lean conditionlikely
• Ignition fault on cylinder 3, such as a worn spark plug or weak coil, upsetting the combustion feedbackpossible
• Mechanical problem on cylinder 3, such as low compression, a burnt or sticking valve or heavy carbon build-up on the intake valvepossible
• Fuel supply fault such as low or unstable fuel pressure affecting the whole engine but showing first on one cylinderrare
• Exhaust leak or sensor fault upstream of the catalyst giving misleading mixture feedbackrare

How to diagnose

1. Read all stored and pending codes and the freeze frame data, noting engine load, temperature and whether the trim was at the rich or lean limit.
2. Check for other codes such as misfires, injector circuit faults or bank fuel trim faults, and deal with those first as they may be the root cause.
3. Inspect the cylinder 3 injector connector, wiring and earth/feed for damage, corrosion, chafing or poor pin tension.
4. Compare live fuel trim and misfire counts for each cylinder at idle and under light load to confirm cylinder 3 is the outlier.
5. Inspect intake hoses, manifold gaskets and vacuum connections near cylinder 3, using a smoke test to find any air leak.
6. Check fuel pressure against the manufacturer's specification, as the method and values depend on the engine and fuel system.
7. Swap the coil and spark plug, or where practical the injector, with another cylinder and see whether the fault follows.
8. Carry out a compression or leak-down test on cylinder 3 and inspect the intake valve for deposits if the engine is direct injection.

How to fix

• Repair or replace damaged wiring or connectors to the cylinder 3 injector.
• Clean or replace the cylinder 3 injector if testing shows it is blocked, leaking or out of flow range.
• Seal the air leak by replacing the faulty hose, gasket or seal.
• Replace worn spark plugs or a faulty ignition coil on cylinder 3.
• Repair the mechanical fault (valve, seat, ring or deposit build-up) if compression or leak-down results are poor.
• Correct any fuel pressure fault found, following the manufacturer's procedure for that engine.

Can I keep driving?

Nearby codes

• P02A1GenericCylinder 2 - Injector Leaking
• P02A3GenericCylinder 3 - Fuel Trim at Min Limit