Vacuum leak at the intake manifold runner or gasket near cylinder 6; Leaking or clogged fuel injector for cylinder 6; Intake valve or valve seat problem specific to cylinder 6; Worn spark plug or ignition coil causing incomplete combustion on cylinder 6; Exhaust leak upstream of the oxygen sensor affecting that bank's trim reading; Faulty oxygen sensor or contaminated sensor signal on the affected bank; Mechanical issue such as low compression or a sticking valve on cylinder 6

DTC codes / P02xx · Fuel and air metering (injector circuits) / P02AE

P02AECylinder 6 - Fuel Trim at Max Limit

Q: What does code P02AE mean?

Cylinder 6 - Fuel Trim at Max Limit. P02AE means the engine computer has reached the maximum authority it can apply to the fuel mixture for cylinder 6, and the exhaust gas mixture is still not correcting as expected. The powertrain control module is reporting that its long-term fuel trim adjustment for that cylinder has hit the calibration limit, which usually points to a vacuum leak, a faulty injector, or a mechanical issue specific to that cylinder.

P02AE means the engine computer has reached the maximum authority it can apply to the fuel mixture for cylinder 6, and the exhaust gas mixture is still not correcting as expected. The powertrain control module is reporting that its long-term fuel trim adjustment for that cylinder has hit the calibration limit, which usually points to a vacuum leak, a faulty injector, or a mechanical issue specific to that cylinder.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyProfessional

AreaFuel and air metering (injector circuits)

Symptoms you may notice

Illuminated check engine light, often with no other noticeable symptoms
Rough idle or a noticeable shake that is worse when the engine is cold
Misfire-like shudder or hesitation under acceleration
Reduced fuel economy as the computer struggles to correct the mixture
A faint fuel or exhaust smell from the tailpipe in some cases
Occasional stalling at low speed or when coming to a stop

Common causes, most likely first

Vacuum leak at the intake manifold runner or gasket near cylinder 6
Leaking or clogged fuel injector for cylinder 6
Intake valve or valve seat problem specific to cylinder 6
Worn spark plug or ignition coil causing incomplete combustion on cylinder 6
Exhaust leak upstream of the oxygen sensor affecting that bank's trim reading
Faulty oxygen sensor or contaminated sensor signal on the affected bank
Mechanical issue such as low compression or a sticking valve on cylinder 6

How to diagnose and fix it

Connect a scan tool and record freeze-frame data and long-term fuel trim values for both banks to confirm the fault is isolated to cylinder 6
Perform a visual inspection of intake hoses, vacuum lines, and the intake manifold gasket near cylinder 6 for cracks or loose connections
Use a smoke machine to check for vacuum leaks at the intake runner and surrounding gaskets
Swap the ignition coil and spark plug from cylinder 6 to a neighbouring cylinder and see if the misfire or trim fault follows
Test the fuel injector for cylinder 6 with a noid light and compare its resistance and spray pattern to a known-good injector
Run a compression test and a cylinder leak-down test on cylinder 6 to rule out mechanical valve or piston ring problems
Inspect the oxygen sensor and exhaust system upstream of the sensor for leaks or contamination, and replace the sensor only after other causes are ruled out

What a maxed-out fuel trim really tells you

A fuel trim at its maximum limit does not automatically mean the injector is bad; a small vacuum leak at the intake runner for cylinder 6 can force the computer to add fuel until it runs out of adjustment range.
Technicians often replace the oxygen sensor first, but the sensor is usually reporting a real mixture problem rather than causing it, so confirm the sensor's signal with a scope or live data before condemning it.
A misfire on cylinder 6 from a weak ignition coil can create a false lean condition in the exhaust, pushing fuel trim to its limit even though the fuel system is working correctly.
Exhaust leaks upstream of the oxygen sensor on that bank pull in outside air and make the sensor report a lean mixture, which drives fuel trim to maximum and sets this code without any real intake leak.
On engines with cylinder deactivation, a stuck lifter or deactivation fault on cylinder 6 can cause a mechanical imbalance that the fuel trim system cannot correct, so check for related misfire codes before chasing fuel delivery.

Can I keep driving with P02AE?

You can usually drive the vehicle short distances to a repair shop, but avoid heavy acceleration, towing, or long highway trips because the engine is running with an uncorrectable mixture that can damage the catalytic converter over time. If the check engine light begins flashing or the engine runs very rough, stop driving and have it towed.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.