Leaking or stuck-open fuel injector on cylinder 6; Faulty oxygen sensor or air-fuel ratio sensor biased rich; High fuel pressure from a failing fuel pressure regulator or restricted return line; Wiring or connector issue causing the injector to stay energized; Engine control module software or calibration error (rare); Mechanical issue such as low compression on cylinder 6 causing incomplete combustion

DTC codes / P02xx · Fuel and air metering (injector circuits) / P02AF

P02AFCylinder 6 - Fuel Trim at Min Limit

Q: What does code P02AF mean?

Cylinder 6 - Fuel Trim at Min Limit. P02AF indicates that the engine control module has detected the fuel trim correction for cylinder 6 has reached its minimum limit, meaning the computer is maxing out its ability to lean out that cylinder. This typically points to a rich-running condition on cylinder 6 that the system can no longer compensate for, often due to a leaking injector or excessive fuel delivery.

P02AF indicates that the engine control module has detected the fuel trim correction for cylinder 6 has reached its minimum limit, meaning the computer is maxing out its ability to lean out that cylinder. This typically points to a rich-running condition on cylinder 6 that the system can no longer compensate for, often due to a leaking injector or excessive fuel delivery.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaFuel and air metering (injector circuits)

Symptoms you may notice

Illuminated check engine light, often with no other noticeable symptoms
Rough idle or misfire sensation, especially when the engine is cold
Decreased fuel economy and a rich exhaust smell
Black sooty exhaust smoke or blackened spark plug tip on cylinder 6
Possible hesitation or stumble during acceleration
Failed emissions test due to high hydrocarbon or carbon monoxide levels

Common causes, most likely first

Leaking or stuck-open fuel injector on cylinder 6
Faulty oxygen sensor or air-fuel ratio sensor biased rich
High fuel pressure from a failing fuel pressure regulator or restricted return line
Wiring or connector issue causing the injector to stay energized
Engine control module software or calibration error (rare)
Mechanical issue such as low compression on cylinder 6 causing incomplete combustion

How to diagnose and fix it

Scan all stored codes and freeze-frame data to confirm P02AF and check for related misfire or fuel trim codes
Inspect the spark plug on cylinder 6 for black soot or fuel fouling, which indicates a rich condition
Perform a fuel injector balance test or swap the cylinder 6 injector with another cylinder to see if the code follows
Check fuel pressure with a gauge and compare to manufacturer specifications
Test the oxygen sensor or air-fuel ratio sensor response with a scan tool to rule out a biased sensor
Inspect injector wiring and connectors for shorts to power that could hold the injector open
If all else fails, reflash or replace the engine control module after confirming no other faults

When fuel trim hits the limit on one cylinder

A single-cylinder fuel trim limit code like P02AF often results from a leaking injector that dribbles fuel even when commanded closed, which is easy to miss if you only check overall fuel trims.
Many technicians replace the oxygen sensor first, but a biased sensor usually affects the entire bank and sets a bank-specific code rather than a single-cylinder code.
Low compression on cylinder 6 can cause unburned fuel to pass into the exhaust, making the oxygen sensor report a rich condition and driving fuel trim to its limit.
The code does not always mean the injector is faulty; a stuck-open purge valve or high fuel pressure can affect one cylinder more than others due to intake manifold tuning.
After repairs, clear the codes and perform a drive cycle that includes idle and steady cruise to verify fuel trim returns to normal before returning the vehicle.

Can I keep driving with P02AF?

You can usually drive the vehicle short distances to a repair shop, but avoid heavy acceleration or prolonged driving because a rich condition can damage the catalytic converter and waste fuel. If the check engine light flashes or the engine runs very rough, stop driving and seek immediate service.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

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