P02CF: Cylinder 2 Fuel Injector A Offset Learning At Max Limit
What to do
Say whether the engine is rough at idle but smooth once you are moving. That pattern is characteristic of this fault and genuinely helps confirm it.
Ask whether the injector calibration codes are right for the cylinders they are on. If another cylinder has an opposite fault stored, two injectors carrying each other's codes is a likely explanation — and that is a coding correction, not a parts bill.
Ask about fuel contamination and the age of the fuel filter, since debris or water narrows the injector's spray holes and produces exactly this.
Do not run it like this for months. A cylinder receiving less fuel than its neighbours runs hotter, and on a diesel that can damage the piston.
What this code means
The correction the module applies to cylinder 2's injector has reached the top of its adjustment range.
The module has been adding as much fuelling correction as it is permitted to on cylinder 2, and the cylinder is still under-delivering. The trim has run out and the shortfall remains.
Under-delivery on a single cylinder produces a specific and recognisable behaviour worth knowing, because it helps confirm the diagnosis before anything is dismantled. The engine is roughest at idle and light load, and smooths out under power. At idle the per-cylinder contribution is small and one weak cylinder is obvious; under load every cylinder is delivering far more and a fixed shortfall matters proportionally less.
A driver describing 'rough when stopped at lights, fine on the motorway' is describing this.
The causes are the under-delivery set: a restricted nozzle, a slow-opening solenoid or piezo stack, a wrong calibration code, or contamination that has narrowed the spray holes.
Where an engine has this on one cylinder and a minimum-limit code on another, suspect the calibration codes before suspecting the injectors. Two injectors carrying each other's codes push their trims to opposite limits, and nothing is mechanically wrong at all.
Prolonged under-delivery is not harmless. A cylinder that runs lean of its neighbours runs hotter, and on a diesel that is a route to piston and glow plug damage rather than merely a rough idle.
Likely causes
Start here
- Blocked or restricted injector nozzle · specialist
- Injector fitted without entering its calibration code · specialist
- Contaminated or poor quality fuel · moderate
Less common
- Injectors swapped between cylinders · specialist
- Failed fuel injector · specialist
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
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