Cause
Air in the high-pressure oil circuit
Air trapped in the high pressure oil circuit that actuates the injectors, which cannot be compressed usefully. The circuit relies on oil being incompressible — air in it absorbs the pump's work as compression rather than transmitting it, so pressure builds slowly or not at all.
Its signature is a hard start that improves with cranking. Each stroke purges a little air, so the engine catches after a long crank and then runs acceptably — and refuses again after standing. That pattern distinguishes it from a worn pump, which fails consistently rather than improving as it works.
Air arrives through the same paths that oil leaves. A failed injector seal, a loose standpipe, a leaking fitting or a low reservoir will let air in as the circuit bleeds down when the engine stops. So air and a leak are usually the same fault seen from two sides, and purging without finding the entry point means meeting it again the following morning. Check the reservoir level and look for a joint that has been disturbed before pursuing the pump.
Typically a moderate job.
Some of these codes mean you should stop driving
2 of the 3 codes this can cause indicate a fault where continuing to drive risks damage or is unsafe. Which one you have matters more than the cause does — read the code's own page before deciding.
Codes this can cause (3)
Codes where this is a likely explanation first, rather than merely a possible one.
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
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.
Others who found this
Be the first to write this up
Nothing posted about this yet. Whatever you found is worth writing down — even a dead end saves someone the same afternoon.
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.
Sign in or create an account to add what you found about Air in the high-pressure oil circuit.