P02A6

What it means

P02A6 is the generic code for cylinder 4 fuel trim at its maximum limit. On engines that support individual cylinder fuel trim, the engine control unit has found that the correction needed to keep cylinder 4 at the target air-fuel ratio has reached its limit. This points to a fault affecting that one cylinder, such as a fuel delivery or air supply problem, rather than a fault across the whole engine. The code does not say whether the cylinder is running rich or lean, so freeze frame and live data are needed.

Symptoms

• Engine management warning light on
• Rough idle or a misfire feel on one cylinder
• Hesitation or flat spots under acceleration
• Poor fuel economy or a smell of fuel
• Rough or uneven running on a cold start
• Possible stored misfire codes for cylinder 4

Possible causes

• Faulty or clogged fuel injector on cylinder 4 (leaking, sticking or restricted)likely
• Wiring or connector fault at the cylinder 4 injector, such as high resistance, corrosion or a poor pin fitlikely
• Air leak local to cylinder 4, such as a split intake manifold gasket, a cracked runner or a vacuum hose leak near that portpossible
• Carbon build-up on the intake valves or a burnt or leaking valve on cylinder 4 affecting airflowpossible
• Ignition fault on cylinder 4 (worn spark plug or weak coil) causing unburnt fuel that skews the trim readingspossible
• Low compression on cylinder 4 from mechanical wear or damagerare
• Exhaust leak or a fault in the sensor feedback used to calculate the individual cylinder trimrare

How to diagnose

1. Read all stored and pending codes and the freeze frame data, noting whether the trims were positive (lean) or negative (rich) and the engine load and temperature when it set.
2. Check for other codes, especially misfire codes for cylinder 4 and codes for other cylinders, as a wider fault changes the diagnosis.
3. Inspect the cylinder 4 injector connector, wiring and the intake area for damage, corrosion, loose fittings, cracked hoses and signs of air leaks.
4. View live fuel trim data, both short and long term, at idle and at higher revs to see whether the correction is the same in both conditions.
5. Check the spark plug and ignition coil on cylinder 4, and swap the coil with another cylinder to see whether any fault follows it.
6. Test the cylinder 4 injector electrical resistance and its operating signal, and compare the spray pattern and flow with the other injectors.
7. Carry out a smoke test on the intake system to find any air leak at the cylinder 4 port or manifold gasket.
8. If the fault remains, carry out compression and leak-down tests on cylinder 4, and check the intake valves for carbon build-up if the engine allows access.

How to fix

• Repair or replace the wiring or connector at the cylinder 4 injector.
• Clean or replace the faulty cylinder 4 injector, following the procedure for that engine.
• Replace the leaking intake manifold gasket or any cracked or split hoses, and fix the air leak.
• Replace the worn spark plug or faulty coil on cylinder 4.
• Remove carbon build-up from the intake valves using the method suited to that engine.
• Repair the mechanical fault in cylinder 4 if the compression or leak-down test shows a problem.

Can I keep driving?

Nearby codes

• P02A5GenericCylinder 3 - Injector Leaking
• P02A7GenericCylinder 4 - Fuel Trim at Min Limit