P2201

What This Code Means

Code P2201 indicates that the NOx (nitrogen oxides) sensor signal on bank 1 is out of range. The NOx sensor measures nitrogen oxide concentration in the exhaust and sends data to the DME for SCR (selective catalytic reduction) system control. The fault can be caused by a failed sensor, an electrical circuit problem (open, short, poor contact), or a contaminated sensing element.

Symptoms

• Engine: Reduced power, limp mode
• Warning lights: Check Engine (MIL) comes on
• Driving: Possible increased fuel consumption and worse emissions

Diagnosis and Repair

Step 1: Check the Sensor Circuit

• Visually inspect the connector and wiring for damage, corrosion, and opens.
• Check circuit integrity with a multimeter (resistance, supply voltage).

Step 2: Diagnose the NOx Sensor

• Use ISTA/INPA to read live NOx sensor data.
• Compare the values against reference values (with a healthy SCR system).

Step 3: Replace the NOx Sensor Bank 1

• If the circuit is good and the sensor reads incorrectly, replace the sensor.
• Part numbers: confirm by VIN (for example, 13628522746 for some models).
• After replacement, run the sensor adaptation through ISTA.

Secondary Problems

Ignoring P2201 can lead to:

• Incorrect SCR system operation (AdBlue injection misses, reduced NOx conversion efficiency).
• Clogging or damage to the SCR catalytic converter from incorrect reagent dosing.
• Higher nitrogen oxide emissions, which can cause problems passing emissions testing.
• In rare cases, DME failure from a short in the sensor circuit.