P229E on Mercedes-Benz
NOx Sensor Circuit (Bank 1 Sensor 2)
P229E on Mercedes-Benz vehicles indicates nox sensor circuit (bank 1 sensor 2). Au7o has documented this code across 1 Mercedes-Benz model — most commonly on V-Class. P229E indicates a fault in the NOx (nitrogen oxide) sensor circuit for Bank 1 Sensor 2, which monitors the nitrogen oxide content in the exhaust gas, typically downstream in the SCR/aftertreatment system on diesel engines. It sets when the engine control module detects an electrical problem (open, short, or implausible signal) in this sensor circuit. The vehicle may enter a reduced-power "derate" mode to limit emissions until the fault is repaired. Note: some manufacturers reassign this code (e.g., RAM uses it for a seat back heater sensor, VW for a seatbelt load limiter), so verify against the specific make. Typical repair costs on Mercedes-Benz range from $300 to $900, depending on the specific model and root cause.
Common Causes of P229E
- •Failed or contaminated downstream NOx sensor (Bank 1 Sensor 2)
- •Damaged, corroded, or loose NOx sensor wiring or connector
- •Open or short circuit in the NOx sensor harness
- •Faulty NOx sensor control module
- •Exhaust leak near the sensor affecting readings
- •Problem in the SCR/DEF aftertreatment system causing implausible NOx values
P229E on Mercedes-Benz by Model
Mercedes-Benz V-Class(1 issue)
- AdBlue/SCR System Faults Triggering Limp Mode and No-Start Countdown2015-2020
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.
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View P229E across all makes →Frequently Asked Questions
What does P229E mean on Mercedes-Benz?▼
P229E stands for "NOx Sensor Circuit (Bank 1 Sensor 2)." P229E indicates a fault in the NOx (nitrogen oxide) sensor circuit for Bank 1 Sensor 2, which monitors the nitrogen oxide content in the exhaust gas, typically downstream in the SCR/aftertreatment system on diesel engines. It sets when the engine control module detects an electrical problem (open, short, or implausible signal) in this sensor circuit. The vehicle may enter a reduced-power "derate" mode to limit emissions until the fault is repaired. Note: some manufacturers reassign this code (e.g., RAM uses it for a seat back heater sensor, VW for a seatbelt load limiter), so verify against the specific make. On Mercedes-Benz specifically, this code is documented across 1 model.
What causes P229E on Mercedes-Benz vehicles?▼
Common causes on Mercedes-Benz: Failed or contaminated downstream NOx sensor (Bank 1 Sensor 2), Damaged, corroded, or loose NOx sensor wiring or connector, Open or short circuit in the NOx sensor harness, Faulty NOx sensor control module, Exhaust leak near the sensor affecting readings. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P229E on a Mercedes-Benz?▼
Repair costs on Mercedes-Benz range from $300 to $900, depending on the specific model and root cause.
Which Mercedes-Benz models have P229E documented?▼
Au7o has documented P229E on 1 Mercedes-Benz model: V-Class.