P01CD: Cylinder 2 Injection Timing Performance - Over Retarded
What to do
Ask whether other cylinders have timing faults, and in which direction. If some are late and others are early, the injectors are probably mismatched rather than failed — that is usually a coding correction rather than new parts, and it is worth establishing before anything is ordered.
Ask for the injector calibration codes to be checked against the injectors actually fitted. It costs nothing and on a car with mixed faults it is frequently the whole answer.
Say whether the roughness is worse from cold, which would point at compression or a glow plug on this cylinder rather than the injector.
Mention any injector work done by anyone, including a previous owner.
What this code means
Combustion on cylinder 2 is happening later than the module commanded.
The mechanism is the family's — a late burn, from a late-opening injector, a slow ignition, or coarse atomisation at low rail pressure.
What is worth adding here is how to use several of these codes together, because they rarely arrive alone and the pattern narrows the diagnosis faster than any single one.
- One cylinder retarded, the rest normal — that injector, that cylinder's compression, or that glow plug.
- All cylinders retarded together — something shared. Rail pressure, fuel quality, or a timing reference that has slipped. No injector needs replacing.
- Some retarded and some advanced — this is the interesting pattern, and it usually means the injectors are mismatched rather than failed. A set of injectors with wrong or missing calibration codes scatters in both directions at once, because each is being driven with the wrong assumptions about its characteristics.
That third pattern is the one that gets misread most expensively, because a car with four timing codes in two directions looks like four failed injectors and is usually a coding job.
Check the calibration codes against the injectors actually fitted before anything is removed. It is free, it is quick, and on a car with mixed-direction timing codes it is very often the answer.
Likely causes
Start here
- Injector fitted without entering its calibration code · specialist
- Failed fuel injector · specialist
Less common
- Low engine compression · specialist
- Failed glow plug · moderate
- Low fuel pressure · moderate
Symptoms
Components involved
Information, not instruction
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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.
Community experience
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What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
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