P02AF

Cylinder 6 - Fuel Trim at Min Limit

P02AF is a generic OBD-II powertrain diagnostic trouble code: Cylinder 6 - Fuel Trim at Min Limit. It is logged by the engine control unit when the powertrain monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.

Code
P02AF
Group
Powertrain
System
Powertrain
Severity
Warning (MIL on)
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What P02AF means

P02AF is triggered when the powertrain control module has pushed the per-cylinder fuel trim for cylinder 6 to its minimum negative limit and still cannot reduce the mixture to the target air-fuel ratio. In other words, the PCM is cutting fuel delivery on cylinder 6 to the maximum degree allowed by its calibration, yet an oxygen sensor or combustion-balance sensor indicates the mixture remains excessively rich. This persistent rich condition on a single cylinder most commonly points to a leaking fuel injector that drips or seeps fuel even when commanded off, but it can also be caused by elevated fuel rail pressure driving higher-than-intended flow through a normal injector. A rich mixture on one cylinder causes incomplete combustion, producing elevated carbon monoxide and hydrocarbon emissions, catalyst overload, and over time oil dilution if liquid fuel accumulates in the cylinder and drains past the rings. On direct-injection engines, where per-cylinder trims are measured with greater precision, this code can surface even from modest injector drift. Applies only to engines with six or more cylinders.

Common causes

Most-frequently reported root causes when P02AF is logged.

  • 1
    Leaking or stuck-open fuel injector on cylinder 6 passing fuel when commanded off
  • 2
    Faulty fuel pressure regulator holding rail pressure above specification
  • 3
    Oxygen sensor on the cylinder 6 bank reporting falsely lean, causing the PCM to over-fuel and then clamp
  • 4
    Injector return line blockage trapping high residual pressure in the fuel rail
  • 5
    PCM software fault or incorrect injector flow calibration (requires reflash or updated calibration)
  • 6
    Cracked injector O-ring at the fuel rail side allowing fuel to weep into the port at rail pressure

Symptoms drivers notice

MIL illuminated with P02AF stored
Rich fuel smell from the exhaust, particularly at idle
Black or sooty exhaust smoke indicating incomplete combustion in cylinder 6
Rough idle or cylinder 6 misfire if the rich condition is severe enough to foul the spark plug
Reduced fuel economy as excess fuel is injected and wasted
Possible engine stall or difficult starting if fuel flooding is extreme

How to diagnose P02AF

A typical diagnostic flow when this code is present.

  1. 1
    Connect a scan tool and log live per-cylinder fuel trim data; confirm cylinder 6 trim is pinned at its minimum (most negative) value
  2. 2
    Inspect the cylinder 6 injector for external leakage with the engine off and fuel system pressurised; look for wetness or fuel smell at the injector tip
  3. 3
    Measure fuel rail pressure and compare to specification; over-pressure pushes more fuel through all injectors
  4. 4
    Perform a leak-down or drop test: pressurise the rail, shut the pump off, and observe pressure hold — a rapid drop combined with rich trims indicates an injector leak
  5. 5
    Remove and bench-test or swap the cylinder 6 injector to verify it closes fully when de-energised
  6. 6
    Check the oxygen sensor on the cylinder 6 bank for cross-contamination or slow response that might generate false rich readings
  7. 7
    Clear codes, test drive under the freeze-frame conditions, and verify trims recover before returning the vehicle

Related powertrain codes

Frequently asked questions

Can a leaking injector set P02AF instead of an injector-leaking code like P02B1?

Yes. Some PCM calibrations detect injector leakage indirectly through the fuel trim loop rather than a dedicated injector-leak monitor. P02AF and P02B1 can both be set by the same failed injector depending on how the manufacturer has implemented diagnosis.

Will the engine damage the catalytic converter with a P02AF active?

Sustained rich combustion on any cylinder overloads the catalytic converter with unburned hydrocarbons and CO. Over time this can melt the catalyst substrate, leading to an expensive converter replacement on top of the injector repair.

Is P02AF dangerous to drive with?

It is not immediately catastrophic, but the rich mixture fouls the spark plug in cylinder 6, risks oil dilution, and damages the catalyst. Prompt diagnosis is recommended; avoid extended driving with the code active.

Could a faulty MAP or MAF sensor cause P02AF on just one cylinder?

Global air-charge sensor errors (MAF/MAP) typically shift all cylinders together rather than isolating one. P02AF specifically points to a cylinder 6 imbalance, making a local cause such as an injector leak or cylinder 6 sensor fault more likely.

Disabling P02AF in software

RaceTune can permanently disable P02AF — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.

Permanent
The monitor is disabled in the ECU itself — not just cleared. It cannot return.
Tailored to your file
Each patch is matched to your specific software version — never a one-size-fits-all file.
Reversible
The original file is always preserved. Reflash the stock to return the ECU to factory state.

Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.

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