P02AA

What it means

P02AA means the engine control unit has found that the fuel correction for cylinder 5 has reached its maximum limit. It is trying to add or remove more fuel than it is allowed to in order to hold the target air-fuel ratio for that cylinder, and cannot. The fault may be lean or rich, so live data is needed to see which. How individual cylinders are monitored varies by engine and model.

Symptoms

• Engine management light on
• Rough idle or a noticeable misfire
• Hesitation or poor pull under load
• Increased fuel consumption
• Smell of fuel from the exhaust or a failed emissions test
• Possible additional misfire or fuel trim codes stored

Possible causes

• Cylinder 5 fuel injector partly blocked, leaking or stickinglikely
• Air leak at the cylinder 5 intake port, manifold gasket or a nearby vacuum hoselikely
• Fault in the cylinder 5 injector wiring or connector, such as high resistance or corrosionpossible
• Ignition fault on cylinder 5 (worn spark plug or failing coil) causing misfire and distorting fuel correctionpossible
• Carbon build-up on intake valves or a burnt or leaking valve on cylinder 5 (engine dependent)possible
• Exhaust leak or faulty exhaust gas sensor affecting the reading used for cylinder balancingrare
• Low compression in cylinder 5 from piston ring or head gasket damagerare

How to diagnose

1. Read all stored codes and freeze frame data, noting load, engine speed and temperature when the fault set, and check for related misfire or fuel trim codes.
2. Look at live data for cylinder 5 correction and overall fuel trims to see whether the limit reached is lean or rich, and whether the other cylinders are also affected.
3. Visually inspect the cylinder 5 injector connector, wiring and nearby vacuum hoses and intake joints for damage, chafing, corrosion or splits.
4. Check for intake air leaks with a smoke test, paying attention to the cylinder 5 port and manifold seal.
5. Inspect the spark plug and coil on cylinder 5, and swap the coil with another cylinder to see if any fault follows it.
6. Test the cylinder 5 injector resistance, supply and control signal, and compare its operation or balance with the other injectors.
7. Check fuel pressure and look for exhaust leaks upstream of the sensors to rule out system-wide causes.
8. If the fault stays on cylinder 5, carry out a compression or leak-down test, and inspect the intake valves where the engine design allows.

How to fix

• Clean or replace the cylinder 5 injector, following the manufacturer's procedure for the engine.
• Repair intake leaks by replacing the faulty manifold gasket, seals or vacuum hoses.
• Repair or replace damaged injector wiring or connectors.
• Replace the worn spark plug or faulty ignition coil on cylinder 5.
• Clean carbon from the intake valves or repair valve and cylinder mechanical faults found by testing.
• Repair exhaust leaks or replace a faulty sensor if testing shows it is the cause.

Can I keep driving?

Nearby codes

• P02A9GenericCylinder 4 - Injector Leaking
• P02ABGenericCylinder 5 - Fuel Trim at Min Limit