P02D2: Cylinder 4 Fuel Injector A Offset Learning At Min Limit
What to do
Ask for fuel rail pressure to be checked before this injector is replaced. On a four-cylinder engine this cylinder is at the end of the rail, and a pressure control fault makes it over-deliver without anything being wrong with the injector itself.
Ask whether any fuel pressure codes are stored alongside this one. If they are, they are very likely the same fault, and fixing the pressure may clear this entirely.
Check the oil level and smell it, since over-delivery washes diesel into the sump — a rising level or a fuel smell needs attention promptly.
Ask for a leak-back test on all four injectors rather than a decision based on this code alone.
What this code means
The correction the module applies to cylinder 4's injector has reached the bottom of its adjustment range.
Cylinder 4 over-delivers and the module can trim it no further down.
On a four-cylinder engine this cylinder sits at the end of the fuel rail, and that position matters here in a way it does not on the middle cylinders. Rail pressure fluctuates along the rail as injectors open and close, and the far end sees those pressure waves last. An injector at the end of the rail can therefore be delivering more than commanded because the pressure arriving at it is higher than the module assumes, not because the injector is worn.
Which is why rail pressure control deserves checking before this injector is condemned. A pressure regulator that is slow or a rail sensor reading low both make the far-end injector over-deliver in exactly this way, and neither is fixed by a new injector.
A stored rail pressure code alongside this one is very likely the same fault. Repair that first and re-check the trims before ordering anything.
Where rail pressure is sound, the ordinary causes apply — a worn needle and seat, a leaking injector, or a calibration code that was never entered. The leak-back test separates them and is worth doing across all four.
Likely causes
Start here
- Worn or leaking fuel injectors · specialist
Less common
- Stuck fuel pressure regulator · moderate
- Injector fitted without entering its calibration code · specialist
- Faulty fuel rail pressure sensor · moderate
Symptoms
Components involved
Information, not instruction
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