P2202 on Mercedes-Benz: How to Diagnose & Fix
NOx Sensor Circuit Low Voltage (Bank 1, Sensor 1)
1 Mercedes-Benz model · 1 documented issue · 1 critical · $300-$900 repair
P2202 on Mercedes-Benz by model: symptoms, diagnosis and fix
On Euro 6 W447 diesels the SCR emissions system depends on NOx sensors (before and after the catalyst) and the AdBlue dosing system. A failed NOx sensor, dosing fault, or low/contaminated AdBlue escalates from a yellow warning to a red warning and finally a 'No start in X miles' countdown, after which the engine will not restart once switched off. The vehicle commonly drops into limp mode (restricted speed/power) before that. NOx sensor failure is one of the most frequently cited W447 emissions faults.
Common Symptoms
- AdBlue warning light (yellow then red)
- 'No start in 500 miles' / engine-start countdown message
- Limp mode with reduced power
- Repeated emissions warnings after a basic code clear
How to Fix
Diagnose the specific fault: replace the failed NOx sensor (genuine/OE recommended) or repair the AdBlue dosing/heater/pump as required, top up with fresh AdBlue, then clear codes and reset the SCR warning scenario (e.g. 'Reset SCR Warnszenario'/soft reset in dealer-level diagnostics). Simply clearing codes without fixing the root cause makes the warning return.
Sources for this issue (3)
P2202 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 P2202 mean on a Mercedes-Benz?
P2202 stands for "NOx Sensor Circuit Low Voltage (Bank 1, Sensor 1)." The PCM has detected that the signal voltage from the NOx (nitrogen oxide) sensor on Bank 1, Sensor 1 is lower than the expected operating range. The NOx sensor measures nitrogen-oxide content in the exhaust to manage the aftertreatment system (SCR/DEF on diesels or lean-burn emission control), so a low-voltage fault means the engine controller can no longer trust that reading. This is primarily a diesel and lean-burn emissions code and typically triggers reduced-emissions or limp-mode behavior. On Mercedes-Benz it is documented across 1 model: V-Class.
What are the most common causes of P2202?
The most common causes of P2202 are: Failed or contaminated NOx sensor element (Bank 1, Sensor 1), Short to ground or low resistance in the NOx sensor signal or supply wiring, Corroded, loose, or damaged sensor connector / pins, Open or high-resistance ground or reference circuit causing low signal, Exhaust leak or soot/sulfur contamination affecting the sensor, Faulty NOx sensor control module or PCM/ECM (less common). The specific cause varies by vehicle.
How much does it cost to fix P2202 on a Mercedes-Benz?
Published repair estimates on Mercedes-Benz range from $300 to $900 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.