P242F — Particulate Filter Restriction - Ash Accumulation Bank 1

P242F points at diesel particulate filter (bank 1). The standard definition names the system involved; which part inside it has actually failed is what the checks below establish, cheapest first.

Common causes

The cause is almost always one of a few things. Here they are — P242F rarely comes from anything outside this list:

• Filter loaded with soot from too much short-distance driving
• Regeneration repeatedly interrupted
• Differential pressure sensor or its pipes blocked
• Additive or fuel-vaporiser fault
• Engine fault producing excess soot

Where to start

In the order a sensible mechanic would work — the cheap checks first, the expensive replacements only after:

1. Check for other engine codes first — a DPF blocks because something upstream is making soot
2. Inspect the differential pressure sensor pipes for soot blockage; they block far more often than the filter itself
3. Attempt a forced regeneration with diagnostic equipment
4. Take the car for a sustained motorway run if a regeneration is pending
5. Clean or replace the filter only once the cause of the sooting is fixed

That is what holds for P242F in general. From here it depends on your engine — tell me which car it is and what it does, and I will give you the steps for it: real procedures, torque figures and diagrams instead of general advice.