P24A2: Particulate Filter Regeneration Incomplete Bank 1
What to do
Try a proper drive first: half an hour at a steady speed on a main road, in a gear that keeps the engine turning reasonably fast. That is what a regeneration needs, and it clears this code more often than any repair does.
Do not switch the engine off if you see signs a regeneration is running — a cooling fan working hard, a hot smell, the idle sounding different, or the stop-start system declining to work. Interrupting it is what caused the code.
Check the oil level on the dipstick, and treat a level above maximum as urgent. Repeated aborted regenerations put diesel into the oil, and an over-full sump on a diesel engine can lead to it running on its own oil.
Keep at least a quarter of a tank of fuel. Many vehicles will not attempt a regeneration below that, which quietly guarantees this code returns.
What this code means
A particulate filter regeneration started and did not finish.
This is one of the most common diesel codes in normal use, and it is very often not a fault at all. A regeneration takes fifteen to thirty minutes of sustained running. Switching the engine off partway through — arriving home, stopping for fuel, sitting in traffic — aborts it, and enough consecutive aborts set this code.
So the first question is always about how the car is used, and the answer resolves a large share of these without a spanner being lifted.
Where the driving pattern is not the explanation, the module was prevented from completing the cycle by something else.
- Insufficient fuel level stops many vehicles attempting or continuing a regeneration at all.
- Coolant temperature never reaching target, usually a thermostat stuck open, means the conditions are never met.
- A fault elsewhere in the emissions system inhibits regeneration deliberately, so a stored EGR or turbocharger code can be the real cause of this one.
- A genuinely blocked filter cannot complete a regeneration, and at that point the code becomes a symptom of the blockage.
Repeated incomplete regenerations do cumulative harm even though each one is harmless. Fuel injected for a regeneration that is then abandoned drains past the rings into the sump, and oil level rising above maximum on a diesel is a genuine hazard rather than an inconvenience.
Likely causes
Start here
Less common
- Low fuel level preventing regeneration · easy
- Thermostat stuck open · moderate
- Particulate filter heavily loaded with soot · moderate
Symptoms
Components involved
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.
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