P246C: How to Diagnose & Fix — Diesel Particulate Filter Restriction - Forced Limited Power
2 vehicles · 2 makes · $200-$3,500 repair
How to diagnose and fix P246C: most-reported vehicles
Ranked by owner reports. Each card gives the symptoms, how to confirm the cause, the fix, parts and sources for that vehicle.
Audi A3 · 2010–2015
The DPF can become clogged, especially with city driving and short trips that don't allow for proper regeneration cycles. This is more common after the emissions fix was applied. A clogged DPF causes reduced power and warning lights. OEM DPF assembly part numbers: 1K0254706LX (earlier production) and 1K0254708GX (later production). Fits 2010-2013 Audi A3 TDI with CBEA/CJAA engines. DPF differential pressure sensor: available from KermaTDI for CJAA/CKRA engines.
Common Symptoms
- DPF warning light
- Reduced power (limp mode)
- Increased fuel consumption during regen
- Strong exhaust smell during regen
- Check engine light with DPF codes
How to Fix
Allow DPF regeneration by driving at highway speeds (65+ MPH) for 15-20 minutes regularly. For forced regen via VCDS: go to adaptation, enter security code 12233, change channel 18 from 0 to 1 while maintaining highway speed. Monitor soot levels via VCDS (Particle Filter Carbon Mass). If severely clogged, professional DPF cleaning with Liqui Moly 20110 DPF Cleaning Fluid (used with 20112 DPF Cleaning Flush and 7945/7946 spray tools) can help. Note: cleaning removes soot only, not ash - ash accumulation requires DPF replacement. OEM replacement DPF often back-ordered for weeks.
Sources for this issue (1)
GMC Sierra 3500HD · 2011–2022
The Duramax diesel DPF becomes clogged with soot under low-speed, short-trip, or heavy towing duty cycles that prevent complete passive regeneration. Owners report the truck entering limp mode, reduced power, and repeated active regen cycles that fail to fully clean the filter. GM TSB 14-06-04-003 addresses regen strategy calibration updates for LML and L5P engines.
Common Symptoms
- Reduced engine power / limp mode activation
- DPF warning light or message on DIC
- Frequent or incomplete regen cycles with elevated exhaust temps
- Excessive fuel dilution in engine oil
- Sulfur or burning smell from exhaust during failed regen
How to Fix
Forced active regen via Tech 2 or MDI scan tool; if clogging is severe, DPF removal and professional cleaning or replacement. Updated ECM calibration per TSB 14-06-04-003. Replacement DPF (ACDelco 84031507 or OEM equivalent) runs $800–$2,500. Extended highway driving after software update can restore function in mild cases.
Sources for this issue (1)
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P246C 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 P246C mean?
P246C stands for "Diesel Particulate Filter Restriction - Forced Limited Power." This diesel emissions code sets when the engine control module detects that the diesel particulate filter (DPF) is so restricted with trapped soot or ash that exhaust backpressure has passed a calibrated limit, and it commands a forced reduced-power (limp) mode to limit exhaust flow and protect the engine and filter. The DPF captures soot from the exhaust and periodically burns it off in a process called regeneration; this code generally means something has been preventing successful regeneration. Ignoring it can lead to eventual filter damage.
What are the most common causes of P246C?
The most common causes of P246C are: Excessive soot buildup from too many short trips that block regeneration, Faulty DPF differential pressure sensor or clogged sensor hoses, Failed or incomplete regeneration cycles, Faulty exhaust temperature sensor, EGR system fault increasing soot production, Fuel injector or other engine fault causing heavy soot, Physically clogged or aging diesel particulate filter. The specific cause varies by vehicle.
How much does it cost to fix P246C?
Repair costs for P246C range from $200 to $3,500, depending on the vehicle and root cause.
Which vehicles are affected by P246C?
Au7o has documented P246C across 2 vehicle models from 2 manufacturers: Audi, GMC.
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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.