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P codepowertrainMedium severity

P2202NOx Sensor Circuit Low Input (Bank 1)

The Bank 1 NOx sensor signal circuit is reading below its expected voltage range, indicating a short to ground or a failed sensor.

Definition

The engine or aftertreatment control module monitors the NOx sensor on Bank 1, which measures oxides of nitrogen in the exhaust to manage SCR dosing or lean-burn NOx trap regeneration. P2202 sets when the sensor's signal circuit voltage stays below the minimum plausible threshold, typically from a short to ground, a wiring fault, or an internal sensor failure. Most NOx sensors are smart sensors with an integrated module that reports over CAN, so supply, ground, and network faults can all trigger this code. Expect a MIL; on diesels, an unresolved fault can suspend accurate DEF dosing and eventually trigger SCR inducement torque or speed derate.

Common causes

  • Failed NOx sensor (internal element or sensor module fault)
  • Signal or CAN wiring chafed and shorted to ground
  • Corroded or water-intruded sensor connector
  • Open or poor sensor ground/supply circuit
  • Exhaust leak or soot contamination damaging the sensor element
  • Control module fault (rare)

Common misdiagnoses

  • DEF (diesel exhaust fluid) injector or dosing module
  • SCR catalyst replaced when only the sensor circuit is faulty
  • Upstream oxygen/air-fuel sensor
  • DEF pump or DEF quality assumed bad without testing

Troubleshooting steps

  1. 1.Scan all modules and record freeze frame

    Note whether companion NOx sensor codes (P2200, P2201, P2204) or CAN communication codes are stored, which points to wiring or network rather than the sensor element.

  2. 2.Inspect the sensor harness and connector

    Trace the harness from the sensor module to the main harness looking for chafe points on the frame or exhaust, and check the connector for green corrosion or moisture.

  3. 3.Verify power and ground at the sensor module

    With the key on, confirm battery voltage on the supply pin and less than 0.1 V drop on the ground circuit at the NOx sensor control module connector.

  4. 4.Check CAN communication to the sensor

    Confirm live NOx ppm data is reported on the scan tool; a sensor that powers up but reports fixed or implausibly low values is failing internally.

  5. 5.Replace the NOx sensor if circuits test good

    Install an OE-quality sensor, since these are calibrated smart sensors, then clear codes and run the required drive cycle or forced SCR readiness test to confirm the repair.

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