P242F: Particulate Filter Restriction Ash Accumulation Bank 1

What it means

The diesel particulate filter on bank 1 reports backpressure attributable to ash (non-combustible residue from oil and fuel additives, not removable by regeneration). The filter has reached the end of its service life and needs cleaning or replacement.

At a glance

• Usually lights the check-engine light
• Affects emissions; the car can fail an emissions test

How it works

The diesel particulate filter (DPF) traps soot in the exhaust; regeneration burns off soot, but leaves behind non-combustible ash. The control module uses exhaust pressure and related data to assess restriction on bank 1, and sets P242F when the restriction is attributed to ash buildup that regeneration cannot remove.

Common causes

Most likely first.

1. Particulate filter loaded with non-combustible ash
2. Excessive ash buildup from oil consumption or additive accumulation

Symptoms

• Check engine light or DPF warning light on
• Power loss / limp mode
• Increased fuel consumption
• Failed forced regeneration attempts

How to diagnose it

1. Record freeze-frame data and DPF pressure, soot-load, and ash-load readings to see the conditions and restriction level when P242F set.
2. Check the service history and engine oil use, since long-term ash accumulation can be accelerated by oil consumption or oil and fuel additives.
3. Inspect the bank 1 DPF pressure-sensor hoses and wiring for blockage, leaks, damage, or loose connections that could distort the restriction reading.
4. Compare pressure readings at the DPF sensor with the manufacturer's specification and verify that the sensor responds as exhaust flow changes.
5. If sensor readings are credible and ash loading is confirmed, have the DPF assessed for off-vehicle cleaning or replacement according to the manufacturer's service guidance.

Common fixes

• Repair or replace damaged or blocked DPF pressure-sensor hoses or wiring on bank 1.
• Replace a pressure sensor that fails its response or specification checks.
• Have the ash-loaded DPF professionally cleaned using an approved process.
• Replace the DPF if cleaning is not suitable or does not restore acceptable flow.

Can I keep driving?

Limit driving, especially at high speed or under heavy load, if power is reduced or the vehicle enters limp mode; the restriction can worsen and increase exhaust temperatures. Arrange prompt diagnosis because regeneration will not remove accumulated ash.