P207F on Mercedes-Benz: How to Diagnose & Fix
Reductant Quality Performance
2 Mercedes-Benz models · 2 documented issues · 2 critical · $400-$3,500 repair
P207F on Mercedes-Benz by model: symptoms, diagnosis and fix
The Sprinter diesel exhaust fluid (DEF/AdBlue) selective catalytic reduction system is plagued by faults in the dosing module, NOx sensors, DEF heater, and SCR catalyst. Failures trigger the dreaded "engine derate" countdown that limits vehicle speed to 5 mph if not resolved, stranding commercial vehicles. The system is sensitive to DEF quality and cold weather.
Common Symptoms
- Check engine light with SCR fault codes
- Engine derate countdown warning on dashboard
- Vehicle limited to 5 mph (derated)
- DEF warning light illuminated
- Higher fuel consumption
How to Fix
Diagnose the specific failed component with Star Diagnostics — the system has multiple failure points. Common repairs include the DEF dosing module, NOx sensors, DEF heater element, and DEF quality sensor. Use only ISO 22241-certified DEF fluid. A full SCR reset with Star Diagnostics is required after component replacement.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- PEAK BlueDEF ISO 22241 diesel exhaust fluid, 2.5 gallonsOEMPEAK DEF002 / ISO 22241-1
Low-level refill or drain/refill after testing confirms the DEF itself is low, contaminated or out of specification Fitment/availability: The inspected direct U.S.
As an Amazon Associate, we earn from qualifying purchases; other part links may also earn au7o a commission. Confirm fitment by VIN before buying.
Owner tips & cautions
- WarningNever use non-certified DEF fluid. Cheap DEF causes crystallization in the dosing module and destroys the SCR catalyst. Buy from reputable suppliers only. BlueDEF from Peak is widely recommended.
Sources for this issue (1)
On diesel GLEs, the SCR/AdBlue emissions system enforces compliance with a start countdown: when it detects a fault it warns 'You can restart the engine X more times,' and once the counter expires the car will not start until the fault is fixed and the counter is reset. The most common root cause is a failed upstream or downstream NOx sensor giving out-of-range readings; other causes are AdBlue crystallization, a blocked dosing valve, or low-quality fluid. Topping up AdBlue does NOT clear the countdown.
Common Symptoms
- 'Start engine X more times' AdBlue countdown warning
- 'Check AdBlue / see owner's manual' message
- No-start after countdown expires
- Check-engine light with NOx/SCR codes
- Reduced power / limp mode
How to Fix
Scan with XENTRY/compatible tool and read live NOx sensor, dosing, and SCR temperature data to pinpoint the failed component. Replace the faulty NOx sensor — OM642/OM651-era downstream sensor is part number 0009058611 (also 000905350364 for the pre-SCR sensor); newer OM654/OM656 diesels use NOx sensor 000-905-48-07 (0009054807). Then have the SCR no-start counter reset (requires dealer/specialist software; it will not clear on its own). NOx sensor part ~$150-350; diagnosis + sensor + reset typically $400-1,200.
Call to confirm they can assess your vehicle and perform the stated work. Search results do not confirm qualification, eligibility or coverage.
Sources for this issue (2)
P207F 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 P207F mean on a Mercedes-Benz?
P207F stands for "Reductant Quality Performance." This code applies to diesel vehicles with a Selective Catalytic Reduction (SCR) emissions system and means the quality of the diesel exhaust fluid (DEF, also called reductant or AdBlue) does not meet the required specification. The SCR system injects DEF into the exhaust to chemically neutralize nitrogen-oxide (NOx) pollutants, and the computer monitors NOx sensors and the DEF quality sensor to confirm the fluid is doing its job. When it concludes the reductant is contaminated, diluted, the wrong fluid, or not reducing emissions effectively, it sets this code. It generally indicates a DEF quality or SCR efficiency problem and often triggers reduced power or limited restarts to force the issue to be fixed. On Mercedes-Benz it is documented across 2 models: Sprinter, GLE.
What are the most common causes of P207F?
The most common causes of P207F are: Contaminated, diluted, or wrong fluid in the DEF tank (e.g., water or fuel), Poor-quality or expired/degraded DEF, Faulty DEF quality sensor, Failing or clogged DEF (reductant) injector, Faulty NOx sensor(s), DEF system or exhaust leaks, Aged or damaged SCR catalyst. The specific cause varies by vehicle.
How much does it cost to fix P207F on a Mercedes-Benz?
Published repair estimates on Mercedes-Benz range from $400 to $3,500 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.