P01CB: Cylinder 1 Injection Timing Performance - Over Retarded
What to do
Say whether the engine is rougher from cold and improves as it warms up. That is the most useful single observation for this fault — worse cold points at compression or a glow plug on that cylinder, while a problem that is the same hot or cold points at the injector. Those are very different repairs.
Mention any glow plug warning or hard starting in cold weather, which supports the first of those.
Mention any recent injector work and whether calibration codes were programmed in, since an injector fitted without its code produces timing faults with a good part.
Expect worse fuel economy while it is unrepaired, because late combustion pushes heat out of the exhaust instead of into the crankshaft.
What this code means
Combustion on cylinder 1 is happening later than the module commanded.
This family adds a direction to the per-cylinder timing codes, and the direction is genuinely diagnostic — over-retarded and over-advanced have different causes and should be read differently.
Over retarded means the burn is late. Three mechanisms produce it:
- The injector opens late. A solenoid or piezo stack that has slowed with age or resistance takes longer to lift the needle after the command arrives. This is the commonest cause and it is specific to this cylinder.
- The fuel takes longer to ignite once injected. That is ignition delay, and it is driven by compression, glow plug performance and fuel cetane. A cylinder with low compression burns late for entirely mechanical reasons.
- Rail pressure is low, so the injected spray atomises more coarsely and takes longer to light.
Distinguishing them is easier than it sounds. An injector that opens late does so at all temperatures. A cylinder that burns late through poor compression or a dead glow plug is dramatically worse cold and improves as the engine warms.
So ask whether the fault is worse from cold. Worse cold and better warm points at compression or glow plug; consistent regardless of temperature points at the injector.
Late combustion wastes energy into the exhaust rather than the crank, so expect poor economy and higher exhaust temperatures.
Likely causes
Start here
- Failed fuel injector · specialist
Less common
- Low engine compression · specialist
- Failed glow plug · moderate
- Low fuel pressure · moderate
- Contaminated or poor quality fuel · moderate
Symptoms
Components involved
Information, not instruction
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