P02D0: Cylinder 3 Fuel Injector A Offset Learning At Min Limit
What to do
Ask for a leak-back test across all the injectors, not just this cylinder. It compares them against each other, takes minutes, and tells you whether one injector has worn out or the whole set is on its way — which is the difference between a repair now and the same repair again in six months.
Check the engine oil level and smell it. A worn injector on this cylinder puts diesel into the sump, and oil above maximum or smelling of fuel needs dealing with promptly rather than at the next service.
Ask whether the calibration codes are correct, since that is the free thing to eliminate before any part is bought.
Do not defer this. The module has run out of trim, which means the wear has been developing for a long time already.
What this code means
The correction the module applies to cylinder 3's injector has reached the bottom of its adjustment range.
Cylinder 3 over-delivers, the module has trimmed it down as far as it is allowed to, and the imbalance persists.
The over-delivery half of this family has one cause that dominates all the others on a high-mileage engine: a worn injector that no longer seals. A common rail injector holds back fuel at very high pressure with a needle and seat measured in microns. As the seat wears, the injector both delivers more than commanded while open and leaks after it closes — and the module sees the sum of the two as excess fuelling on that cylinder.
The leak-back test is what distinguishes this from a calibration problem, and it is the measurement worth insisting on. With the return lines instrumented, an injector leaking past its seat returns visibly more fuel than its neighbours. It takes minutes and it answers the question definitively — where the calibration route only tells you what was programmed.
A worn injector that over-delivers puts diesel down the cylinder wall. Check the oil level and smell: a rising level or a strong diesel smell means fuel is reaching the sump, which dilutes the oil and, in the worst case, lets the engine run on it.
Where several injectors leak back excessively, the set is worn and replacing one is a short-term repair.
Likely causes
Start here
- Worn or leaking fuel injectors · specialist
Less common
- Injector fitted without entering its calibration code · specialist
- Failed fuel injector · specialist
- Reconditioned injector fitted with its original code · specialist
Symptoms
Components involved
Information, not instruction
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