P242F on Mercedes-Benz: How to Diagnose & Fix
Diesel Particulate Filter Restriction - Ash Accumulation (Bank 1)
2 Mercedes-Benz models · 2 documented issues · $60-$2,500 repair
P242F on Mercedes-Benz by model: symptoms, diagnosis and fix
EU-market GLS 350d/400d models with the OM656 3.0L inline-six diesel suffer from sensitivity in the exhaust aftertreatment chain. The EGR (AGR) valve, diesel particulate filter (DPF) and SCR/AdBlue system are sensitive to poor fuel quality, short-trip driving and temperature swings. Clogged DPF, a dirty/sticking EGR valve, or a faulty EGR differential-pressure sensor cause power loss, failed regenerations, dashboard warnings and limp-home mode. A German motor-talk owner thread on the GLS X167 400d documents poor acceleration that resolves after a restart, traced to a replaced EGR differential-pressure sensor under warranty. This primarily affects diesels not sold in the US, so it is especially relevant to the EU market.
Common Symptoms
- Reduced power / poor acceleration
- Limp-home mode
- DPF / exhaust warning light
- Repeated regeneration cycles or failed regen
- Increased fuel consumption
- AdBlue/SCR warning
How to Fix
Drive the vehicle regularly at highway speed/load to allow active DPF regeneration to complete; avoid chronic short trips. Keep AdBlue topped up with spec-compliant fluid. Have a clogged DPF forced-regenerated or cleaned, and replace a sticking EGR valve or faulty EGR differential-pressure sensor as needed. Use good-quality diesel to reduce soot loading. Address fault codes promptly before forced regen damages the DPF.
Sources for this issue (2)
The Euro 6 diesel particulate filter on the W447 needs periodic high-temperature regeneration to burn off soot. V-Class vehicles used for short urban trips never reach regen temperature, so soot accumulates, regen attempts fail, and the DPF eventually clogs. This brings warning lights, sluggish performance, increased fuel consumption and limp mode (capped around 2,500 rpm). The aggressive Euro 6 emissions hardware makes the W447 particularly sensitive to short-trip duty.
Common Symptoms
- DPF warning light
- Sluggish performance / limp mode (~2,500 rpm cap)
- Increased fuel consumption
- Frequent failed regenerations on short journeys
How to Fix
Catch it early with a sustained 30-40 minute motorway drive at 2,500-3,000 rpm to trigger passive regen; if blocked, run a forced/active regeneration with a diagnostic tool. Heavily clogged filters need professional cleaning or replacement. Address any upstream cause (NOx/EGR/injector fault) that aborts regen.
Sources for this issue (2)
P242F code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P242F mean on a Mercedes-Benz?
P242F stands for "Diesel Particulate Filter Restriction - Ash Accumulation (Bank 1)." P242F is a generic diesel emissions code indicating the engine control module has detected excessive restriction in the Diesel Particulate Filter (DPF) caused by ash accumulation rather than recoverable soot. Unlike soot, ash cannot be burned off through normal or forced regeneration, so this typically signals the DPF is reaching the end of its service life and needs cleaning or replacement. The condition reduces exhaust flow and can trigger reduced-power (limp) mode if left unaddressed. On Mercedes-Benz it is documented across 2 models: GLS, V-Class.
What are the most common causes of P242F?
The most common causes of P242F are: DPF at end of service life with accumulated non-combustible ash from engine oil additives, Excessive oil consumption (worn rings/valve seals) loading the filter with ash, Use of non-low-ash (non-CJ-4/low-SAPS) engine oil, Repeated incomplete or failed regeneration cycles over time, Faulty DPF differential pressure sensor giving high restriction readings, Clogged or saturated DPF substrate requiring professional cleaning or replacement. The specific cause varies by vehicle.
How much does it cost to fix P242F on a Mercedes-Benz?
Published repair estimates on Mercedes-Benz range from $60 to $2,500 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
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Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.