P2B95: Cold Start Injection Pulse Performance
What to do
Say whether the engine is rough or noisy only for the first half minute and then settles. That is exactly the window this covers, and it is the most useful thing you can report.
Mention any recent injector work and whether calibration codes were programmed in. An injector fitted without its code produces this with a physically sound part.
Treat it as an early warning rather than a nuisance. The cold-start strategy uses very small, precise injection pulses, and those are the first thing a fouling injector loses — so this appears before anything you would notice in normal driving.
Mention any poor fuel recently or a long period standing unused, both of which leave deposits.
What this code means
The injection pattern the cold-start strategy commanded was not achieved.
This joins the cold-start family the corpus carries elsewhere, and it is the fuelling member of it. Everything in that family serves one purpose: getting the catalytic converter to light-off temperature before the driver reaches the end of the road, because most of a journey's emissions are produced in the first minute.
Injection does its share of that work through the shape of the pulse rather than the quantity. A modern engine does not inject once per cycle — it splits the delivery into a pilot, a main and sometimes a late post-injection. At cold start that pattern changes deliberately: a later main injection puts more heat into the exhaust, and on a diesel a post-injection adds fuel that burns in the exhaust rather than the cylinder.
This code says the commanded pattern was not delivered.
Which points at the injectors and at what they are being given:
- Deposits on the nozzle, which blur the small, precise pulses this strategy depends on. A pilot injection is a very small quantity, and it is the first thing a fouled nozzle loses.
- Rail pressure not established, since cranking is when the pump is slowest and the strategy begins immediately after.
- Calibration codes not programmed, so the module's expectations of each injector are wrong.
A fault confined to the first thirty seconds is an early warning. An injector that cannot deliver a small pilot pulse today will struggle with a main injection later.
Likely causes
Start here
- Blocked or restricted injector nozzle · specialist
- Worn or leaking fuel injectors · specialist
Less common
- Injector fitted without entering its calibration code · specialist
- Low fuel pressure · moderate
- Contaminated or poor quality fuel · 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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